I've generated quite a few runtime graphs (without additional cooling) using the P1, and I have not noticed any problem with the P1. At least, there does not appear to be any short term problem running the P1 for 2 ~ 2.5 hours at a time.
P1 was clamped using a small vice for the runtime tests, and the light did not appear to get too warm or hot.
Long term effect (if any) is unknown at this time.