The reason bulk REGISTER OFF is slow is that LISTSERV aggressively trims the
SIGNUP files when records are deleted. The goal is to keep the files small,
and under normal conditions there are no bulk de-registrations. You would
not normally have a trim more often than once a minute at the most, probably
more like once every 5 minutes. Each individual trim is normally a fraction
of a second, the problem is when you chain them as fast as possible.

The main impact of having too much SIGNUP data is that you waste some disk
space (probably not a concern nowadays) and that you need to increase the
number of individual files (SIGNUP_HASH) to retain the same level of
performance. Other than that, it is no big deal. Very few sites are
SIGNUP-constrained. You need an unusual kind of workload to run into that
problem. Of course, if you did notice a performance problem with SIGNUP data
access, it could make sense to schedule some downtime to deregister the
addresses.

  Eric