With just one Block Erupter USB it really doesn't matter. Just start your mining program, put a fan on the BE, minimize the program and forget about it.
I would probably solo mine with one device and check it once a year just for giggles.
Have Fun,
Sam
Actually, I'm mining with just one on btcguild. It comes in handy for answering questions like "how much will I make with one of these?" i just look at the 24 hour earning number. Also, I payout every .05 BTC and use the time between payouts to calculate how long to earn 1 BTC. It is about 280 days at the moment. The numbers are rough because there is occasional down time, but i find it interesting just the same.