I don't really like this strategy - leads to regrets for me. Only sell if you think you have somewhere better to invest the money or if you truly think the company is overvalued after adjusting for risk.
It's really hard to resist the sell urge when you are up, but if I had resisted, I would still own NGLS (sold at 11, now 20), GLS (sold at 3.75, now 8.5), CEP (sold at 3.2, now 4.3), XTEX (sold at 6.25, now 6.8), ETFC (sold at 1.32, now 1.69), BEE (sold at 1.1, now 2.3), BBEP (sold at 6.5, now 12.3). For all of those, I still thought they were undervalued but I sold anyway just because I was up a fair bit.
For EROC, I think it's worth $8 adjusted for risk and I'm sticking by my guns on my valuation unless we get some bad news.
I think you're right on EROC, but I never beat up myself for selling, because that was an informed call at the time. I sold SHO at $6+, AVI at $9+, ATL(S) below $10 (yeesh) and that turned out to be way wrong, but I was sober when I sold them. Besides, you have to consider what you've done with the proceeds since then, and I killed. A lot of that money ended up finding its way into EROC in the low $3's and XTEX in the $3.70's. Never look back.