I was told at some point that Sun used UDP for NFS for that reason. It was a reasonably big deal when we started to move to TCP for NFS ca 1990 (my memory of the date -- I know I did it on my own for SunOS as an experiment when I worked at the SRC -- it seemed to come into general use about that time).

What kind of numbers for TCP connections would be reasonable in 1980, 90, 2000, 2010? 

I sort of think I know, but I sort of think I'm probably wrong.