I mined back in the CPU days, solo mined a few blocks of 200btc each.  Once GPU mining started, i dropped off the radar for a few years and then got a very early buy with BFL.  after waiting nearly a year i got my 2 jalapenos (the 7.5GH upgrades ones) and made all of the money back on those in like 2 weeks.  Since then it's been all profit and even now I would not shut them down. The electricity use is tiny, i have them run by a low power laptop, and it gives me more btc to spend.