Removing old revisions

[John]

I am wondering about removing old revisions from our files in cvs.  One of
our managers thinks that be retaining all of the old revisions we are
incurring overhead in our cvs interactions.  We have rather large
repositories and quite a few of the members have many revisions.

It seems to me that I recall reading someplace in the past that removing old
revisions is not a very wise thing to do. Does anybody have any thoughts or
advice on this subject?  Is it a common practice or not?  Is it dangerous? 
Is there any performance degradation by not removing old revisions?

Thanks you,
John Elgin