I tested my 5mW Opto with fresh Duracell alkalines and with fully charged Duracell NiMh AAAs. The output power of the alkalines was about 22-23mW after switching the laser on, but dropped at a steady rate to about 18mW in a minute. The NiMh AAAs never touched 22mW, but do not drop in power like the alkalines do. Overall about 19-20mW measured in a minute.
In that case, let's hope you'll get a overspec one. Or, you could somehow try to cough up the $27 the 30mW Opto costs more then the 5mW, and hope that one will be overspec as well. You'd probably want some safety goggles with that one.
I can vouch for the 5mW version being over spec at times. I also have one and I think it put outs 20 to 25mW maybe even close to 30. I've found that rechargable batteries suck with mine though. It takes a while to warm up and never seems stable with them. I've tried normal batteries and lithiums though. The lithiums are the best IMO. They last a long time and the power doesn't seem to drop until the batteries are about dead.
The pointer Petrovski got is not the typical 5mW, usually the premium 5mw is 5.0 to maybe 8mw on the high end.
I was running out of the premium 5mW units a while back and ended up sending out below spec. 30mW ones in there place as those were anywhere between 10-30mW. I also had a couple 5mW ones that did put out ~15-20mW that I was holding onto and sent them out as well.
Since then a new shipment has arrived, so if a premium 5mW is ordered you'll most lkely get one that outputs between 5-10mW.
If you have some friends who want to get a pointer as well, were now offering 3-packs of both the 30mW and 55mW that are at a 20% discount of the single unit price, so that could be an option as well.