The refined techs as StevenAus said, is used to spend your research points, when you are finished researching everything else. As such you can research the refined techs infinitely, meaning you get the bonus everytime you are finished researching them. For example refined agriculture gives you a bonus of +5 to food per grain. Researching this for example two times gives you an additional 1o food per grain to your cities. As such you can use refined agriculture to get your cities to level 4 or 5, if you do it many times.
So as StevenAus said it is not really wasted as you have gained additional food in your cities.