I’ve slept with a vacuum ADS on many occasions without incident, but I think there’s a big difference between a vacuum ADS and a pump.
First, a pump cylinder cuts into the skin around the base of the penis. Over the course of an entire night, some significant damage could accrue (although the pain would probably wake you up).
Second, a pump may impair circulation. I’m not positive about this, however. In some ways, being in the pump may improve circulation. The only way to know for sure is to try pumping at low pressure and see how you feel as time goes by. If you can stay in a pump during the day for 10 hours without a problem or any funny feelings, chances are it won’t be a problem when you’re sleeping. But who knows. It seems like the risk is high.
Third, a pump’s pressure is generally not well regulated. Slight movements during the night could increase of decrease the pressure significantly. Even if you’re confident that 2” HG won’t hurt for 10 hours, 3 or 4” might, and you wouldn’t necessarily know you had a problem until you woke up.
Another point to consider is the value of night-time erections for girth gains. I think they might play an important role. I think an easier and safer alternative to pumping during the night is to take a hit of Cialis, look at some porn, get yourself smoking hard, and just go to sleep. You’ll probably have lots of strong erections during the course of the night, and they will do wonders to promote your girth gains.
You might want to skip the Cialis, especially if your PE routine has improved your erection quality. Simply going to sleep horny with a raging hard-on will probably do the trick.
Bottom line: I wouldn’t try sleeping while pumping. It’s too complicated. The potential benefits probably don’t outweigh the risks, and there’s probably a better and safer alternative.