The last time I rebooted my 7204 was for a hardware upgrade (memory and ATM card). 5 years and no failure.
Never have rebooted a 2821 - 12 months.
Never rebooted PIX 525 - 36 months and counting
Rebooted my PC - 2 days ago for instability
ICS is fine if that is what you have to use. But compared to dedicated hardware, well, there is none.