Hello Ian, Erik, all,
ADMBase copies the previous timelevels of its variables to the current timelevel. This is (if MoL is used) repeated by MoL. This is a very fast operation, so it won't cause performance problems.
Before you wonder when that happened: It does so since r48 from January 2010 (it seems). Before nothing was copied. We are about 1 year 7 months too late to complain about *that* change :-)
Yours, Roland