wtmp backup script - howto change "how often"

["Peto V." <konfery@lentus.sk>]

Hello.
I'm using unstable & I don't like "settings" of logrotate-I mean "backing
up of /var/log".
For example:
I wanna wtmp to be backed up 1/year (or 1/month), but (!) I wanna have
only_one wtmp for all year (eg 2004).
I think, its simple and i have to just change something (simple) in
logrotate script (or somewhere else).
(in case I "invent" or "find" something - i dont want to mess up logs or
backingup logs etc.)
What & where should I change?

TNX for help

Peter