Ah, herein lies the rub. Indeed I find that the laser will only run at 100% power for about 10 minutes before both it and the power unit overheat. The laser looses power as the temp exceeds the critical point until it is in the sub 1W (I’m guessing) range.
Additional cooling (more fans, better airflow,) helps extend this period. Better yet is to run the unit at lower power where it can run many times longer. The primary reason I sprung for the 15W is so that I could run it at 1/4 power and still have a more powerful laser than the 2.5W laser I was using.
Personally, I just don’t view this as a significant cutting or metal etching laser. I use it for burn engraving wood, leather and plastic and it’s great. Small cutting jobs, or jobs broken into sections that allow cooling periods, or multiple passes at reduced power are how I handle the (primarily leather) cutting I do.