well, no and yes.
or even yes and yes.
or then no and no
basically, long online hours can affect the speed as there might be trashy programs not releasing their used memory.
and wintosh can do that too.
we had a PDC with IIRC NT sp4 on it and it kept using it's memo up until it had to be rebooted after some days.
basically, the OS itself can sit fine online for about 6-12 months without any harm.
but then again, it can't be properly updated up to date without reboots.
nor can all the stuff be released.
like, with w2k I've seen that after some 7 days it brakes down something in it's network-part and can't use VPN anymore.
and restarting all services does not help either.
like you propaply see, it's kinda yes/no answer.
but if you like to present your boss a draft that all comps need to be shutdown to keep them healthy, that does comply.
basically normal client with normal env should run just fine months without any problems.
_________________________
!download
KiXnet