changing long to DWORD doesn't really fix the overflow issue.
The fundamental problem is that some of the apis, e.g. WaitForSingleObject have a DWORD maximum.  so, we cannot support sleep times longer than some particular time.

Microseconds was chosen in the api because that is the resolution of the api in pthreads.

IMHO, I think it is okay to have an implicit ceiling on the timeout, e.g. some 4000 seconds.  We can add a caveat somewhere that anyone intending to sleep for extended periods of time should be prepared for a timeout occurring early, and should have his own timing logic to deal with that.

My suggestion then is to 
a) change the apis to DWORD
b) add a macro something like PyCOND_MAX_WAIT set to 2^32-1
c) properly clip the argument where we call this cunfion, e.g. in lock.acquire.