Power no; Home yes
I have worked on a few iPhone 4 handsets.
None had -this- problem with the power switch.
The phone I'm using now, is 2.5 to 3 years old.
I had it totally apart once for screen, back, battery, charging dock, home button replacement, AND used it as a test bed for half dozen replacement cameras I bought.
The power button continues to work fine.
What I -DO- notice, is regular failure of the Home button.
They're good for about a year.
I always replace it when I put on a new screen.
My phone is currently overdue for its 3rd home button right now!
I see the Home button assembly is improved on the 4S.
Probably to keep out dirt, finger oils, makeup, etc.
I'm still looking for a 4S to use, so I don't have any data on them.
(a broken one would be fine, if ya got one)