You would be better off using the search function, as there have been slightly over a million threads on this subject.
The modern school of thought appears to be that all exercises are a waste of time and sufficient dexterity and technique can be obtained by playing actual pieces. Actual finger inpedendence is supposedly impossible and can be overcome with wrist rotations. Anti-Hanonist thought, is that playing these pointless exercises without the supervision of a teacher is dangerous and can eventually lead to injury.
The old school of thought is that the playing of exercises will build a solid technique. If you can play all Czerny, Hanon and Pischna, you can supposedly play anything and the exercises practiced often, will force an independence into the fingers and will eventually lead to an all round mechanical ability.
Anyway, you are better off doing some research into previous posts than to rely on my fading memory.
For what it is worth, I have stopped using Hanon and i have noticed no decay in my abilities, but also no improvement either. I admit to warming up with a combination of trills in single notes, thirds and sixths.
Thal