At what point should I limp in the small blind?

[defence18]

I thought I read, although I can't remember where, that you should not play a small blind hand unless it is a hand you would normally play. That used to make sense, but since I started playing micro-limits, I've noticed that for me to call in the small blind when there hasn't been a raise, I'd be getting 7-1, 8-1, 9-1, or even 10-1 odds to call. At that point, should I call the small blind and try to catch a good flop with bad hands, or should I muck? In other words, is calling here with hands like T7o or 85o a +EV play with those odds?