The four biggest battery drains on these devices are (in no particular order):
Screen (especially on the IPS+ when set to max)
The battery modes limit the processor.
Normal - 1.3 GHz max CPU speed
Balanced - 1.2 GHz max CPU speed
Power Save - 0.8 GHz max CPU speed
You will have slightly extended battery life, but I bet it is not that noticable.
On my TF101 (default clock speed of 1 GHz) and have it overclocked to 1.4 GHz and have not noticed any major difference in battery life (maybe 15 instead of 16 hours). Even setting it to max clock of 0.4 GHz (which it runs most apps really really laggy) does not do much for extending the battery life.
Best advice is to keep the screen as dim as you can handle it and that will do the best at extending your battery life.