The limit on Linux is usually a bit under 2MB (ARG_MAX), other Unicies will vary no doubt and Windows is 32KB, and I'm sure you are aware that xargs is your friend.
Yes, xargs works on Unixen. I wonder if there is any equivalent on Windows (other than using Unix xargs via Cygwin etc.), or writing your own? This point didn't occur to me before, but it could be useful.
