Gene
It varies, partly by what I'm doing (things like stippling where you're running full throttle continuously you go through gas faster). Generally I get the 8 - 10 hours of run time advertised. Occassionaly I get a lot less, usually because I either didn't get things tightened properly or they got bumped in the Box. My 'master' 20lb CO2 tank is about half empty and with the cold in the garage I'm having trouble getting a good fill on the small tanks. Got a couple ideas on how to fix it, just need the time.
For engraving in the house do what I do when I'm playing in a hotel - spread an old towel over the work area first to catch the chips. Makes cleanup a breeze because you just put your gear away, fold/roll up the towel and then take it outside to shake it clear. And yes, I have done some work while in the living room.