New upgraded battery

Why can't apple create a new upgraded battery to last like the new model ones for their old macbook alum's? if the life time charging cycle's about due soon (nearly 2 years) Don't ya think People will want replacement batteries to last longer like the new products do? I Really Don't think it's too hard to produce something that has a longer charge time and fit in the space allotted. and stop producing the old type batteries.

Besides my macbook only lasts about three hours which is rather lame.

Message was edited by: Polaritypictures