Bad idea is what I'd say. If you disconnect/reconnect, channel windows can stay open so no conversation is lost (check options).
The only time when this might be nice is when you accidentally quit the program and immediately restart it. This of course would require you to actually click the X and (in my case) confirm the exit. Why would you immediately want to restart it?
That leaves restarting mIRC after a few hours or so. Then there would be no reason to display the last few lines in the logfile - they're several hours old and thus have no value.
