Laser warm up???

hey guys quick question.... what is "warm upp time" for lasers... with my 50 mw greenie the instructions say "warm up time under 2-3 minutes....what does it mean... does that mean dont run it for that long or it will over heat.... or it wont run properly until 2-3 min??????

it means that it takes 2 or 3 minutes to reach full power.

..... thanks mate... i was worried bout overheating it.... lol