I'd really like to know how you got them numbers currently been mining 07:16 hours i've already earned 0.02128931 with my Block Erupters with Bitminter so thats about $6 of my investment back already.
There is no way that you mined 0.02 BTC in 7 hours with 10 USB block erupters. Maybe you forgot a couple zeros? At the current difficulty, your 10 miners will mine about 0.0033 BTC a day.
Perhaps you are mistaken and you have 10 Block Erupter
Blades instead 10
USB Block Eruptors. Those are 10 GH/s each, not 336 MH/s. If that is what you have, then you got a very good deal on them and you will break even very quickly.