Thanks, Marcello, for your reply.
Yes, I discovered yesterday that store-and-forward ("mode=forward" in
audisp-remote.conf) was implemented in version 2.1, in March 2011.
Unfortunately, it is taking a while to be in Debian and Ubuntu.
The older versions allow you to specify the queue length, but that would
appear to have no effect. It just seemed to be in the format of the
config file in anticipation of store-and-forward being available.
It is audispd that is complaining. Funny that it says "audispd: queue is
full - dropping event" when it is not using a queue.
Anyway, I am left with several possibilities:
1. Upgrade to a recent version (which?), even though the distribution
does not support it.
2. Up the priority-boost in auditd.conf and/or audispd.conf.
3. Write the log locally and then have something monitor the file. What?
4. Can auditd use rsyslog?