Nope, it's not long at all. They, like other arachnids, are masters at staying on "power-save" mode. My good friend has an emp just under 6" long who has been refusing food for four months, still going strong. They really only need a couple crickets a week. I've had my tarantulas regularly refuse prey for two months before each molt. They really don't need a lot of food and can go quite a while without it.
This. I feed my T's (and my buddy's scorp when I take care of it) one good sized cricket (or two smaller ones) once a week, and he does the same with his scorp at home. If they refuse, then they just have to wait til the next week. They've all been doing good.