The convenience of the cordless model outweighs the slim chance that I will have a dead battery. Besides, I have two other Dremel tools, an ancient 35 year old one that's still kicking, and my 4000 corded model. I also use a cordless screwdriver and drill for virtually all of my tasks that require such tools. Somehow, I manage to always have a battery charged and ready, maybe because I think ahead and always have an extra charged battery. My DeWalt inertia screwdriver charger will charge the battery faster than I can run down the second one. Ditto for my Milwaukee cordless drill. I have corded stuff that will fill in, but somehow it rarely needs to come out.
Oh, and my phone is cordless as well, just fits in it's holder and works all day.