Have the AI check overall strength before declaring war.

Difficulty level?

What you're saying makes sense in some ways, but not so much looking at it from another point of view. If you are ahead in economy, industrial potential, and technology, but behind militarily, it makes even more sense for the AI to attack you - how else could they ever possibly win? Maybe you will manage to build a huge, technologically superior fleet before they can take enough to make up for the difference in infrastructure, but at least trying the attack gives them a better chance than doing nothing and waiting for you to turn your economic advantage into a offensive military advantage or win a technological victory or something (now I'm pretty sure the AI doesn't actually think "better attack him or I'm going to lose", but either way the AI's aggressive behavior in the face of a superior economy with fewer ships at the moment makes sense, to me at least.)

Possibly part of the problem is the AI's habit of declaring war then not attacking for weeks and weeks.

It would make sense for the AI to attack when it's behind economically IF the AI were playing like a human trying to win the game. However I read somewhere else (from one of the devs I think, possibly Brad) that the AI is supposed to play like a galactic empire ie. it should do everything possible to prevent you stomping on it.

And yes, the whole 'let's declare war then sit here doing nothing for a while before sending a few unguarded transports towards the enemy' thing doesn't help (ok so I'm still playing with 1.0x not 1.1). However this seems to be something that happens with a lot of TBS's - AI's in general seem to find it hard to grasp the concept of a sneak attack.

Well maybe have a different setting for each AI? So the Drengin would look at you, assume that if you were ahead in tech you'd be invading them in a few years (because that's what they'd do), and attack if they felt they had any chance at all, while the humans would be just as happy to let you grow into an economic monster and trade with you. Perhaps the player's alignment could also come into play, so that the AIs would be more likely to attack an evil player who was getting ahead in tech because they would be more likely to be stomping the good guys later. And againg this would be customized for the AIs, so the Altairians would be ready to launch a crusade, while the humans might try appeasement instead. I'm not sure how practical that would be, but I think it would make the most sense.

It would still probably be a better allocation of resources to make sure the computer is effective when it does attack you than to worry too much about when it declares war, though.

Yeah also it seems kind of weird to me that the Altarians will declare war on a fellow good civilization, even if said good civilization is way behind them militarily or in any way for that matter. What kind of good guys are these that will attack their fellow good guys if were wimpy, sounds like a bully to me, and bully's != good..... Of course that might make being good a bit too good (sorry )..... Of course you'd still have to have a military unless your only playing against good civs, cause the bad guys would hate your guts and would be more than happy to invade.

Whats the difficulty level?

trade more and bribe more if you are getting attacked by the AI. Usually just sending one freighter off to everyone and then some extras to your immediate neighbors will help immensely with how likely they are to attack you. Give out (large) bribes of whatever you can afford every so often if your relations start dropping due to military nonexistance, that will usually give you enough time to build up enough of a fleet for them to ignore you a bit longer. It especially helps if you can bribe one of the other AI's into attacking them since it will often put in "too busy to risk war with us right now" in the relations.

Honestly doesnt really matter what difficulty you play at...Even at Painful or harder the AI still declares wars and then does nothing for 20+ turns.

Would be nice for them to declare war much like a human player and take 50% of your planets in the first couple turns:P All they would have to do is park the transports out of sensor range.

Anyway main problem is how the AI decides to invade planets it seems to only actually send a transport if a planet is currently undefended. They dont think ahead and say send transports to your planets while their fleet takes care of your defences. Then again the AI is never strong enough to compete with a human as far as millitary goes so the whole issue is kinda mute...

Honestly doesnt really matter what difficulty you play at...Even at Painful or harder the AI still declares wars and then does nothing for 20+ turns.

For me it's like 4-5 weeks. But much of it is because their ships are so damn slow, you dont notice the 'attack' until much later....

It's funny how when the human player gets to choose a target to attack and the second before he attacks declares war. But the computer AI must declare war first, then start choosing targets.

If only!
I was playing on normal in the Demo, and was focusing on research. Then the Drengin decided to declare war. I had no Ships and not military starbases so I had to quick build. Luckily I had better techs so I was able to punch out a fleet of three ships to tackle theirs (which arrived 2 turns after they declared war) that outmatched their weaponry 3:1. They lost that battle, but sent transports in anyway, so I surrounded my home planet with ships and awaited the next attack.... oops.
The problem is that I was thinking that the AI was going to be stupid, and continue attacking my homeworld since it was closest to the border.
What They did was send a couple transports around the long way (seriously far out of the way) around my sensors and captured my two highest producing planets, leaving me with Earth and Mars. I surrendered to the Altarians.
The entire War took maybe 15 turns.

On other games, though I have noticed them doing the "Military might glitch." However I argue that attacking like that is not the best resort. It would be better to form an alliance with the other races and attack en Mass. A Quick assault by a large group could sigificantly cripple just about anyone before they can build up.

You should align as evil, or play as the Drengin or Korx and watch what happens. The Torians and the Altarians always go after you and the damn Torians do NOT screw around when they launch an invasion. MASSIVE...... fleets of troop ships. And they escort them now in 1.1. So no more running around with an armed cargo hull popping helpless transports.

So it doesn't really matter if they hit you right away or declare war first several turns ahead of the attack. When the Torians come after you, you better be ready for them.

I would rather they watch the position of their ships before declaring war.

Sometimes, they declare war, then take a lot of turns before you even start seeing anything remotely aggressive. I presume it's because they have slow slow ships, it takes ages before the aggression begins.