The problem is that early game, you are going to have a hard time making that many caps without hurting yourself in some other way. Capital Ships, while great for a variety of reasons, don't have a very high DPS without a supporting fleet, and so in general, if your opponent rushes you early and you are rushin Cap Ships, you're going to get crushed.
I am a rushing type of player so I guess it doesn't make sense to me that someone would be able to build that many Cap Ships without getting rushed. I have found that early game, you need only 2 Capital Ships to take out a meteor or non-homeworld planet, which, in a 1v1 situation, gives you a huge economic and strategic advantage, at least if you can hold on to it for awhile. After you have taken one of your opponent's planets, and are making sure he doesn't expand anymore, it doesn't really matter how fast you kill his Howeworld, he dies by macro.