I calculated everything and i think i will break after 5-5,5 months... but this calculating is with websites like whatmine.com etc. so i have to still mine scrypt and on night sell them on market and check again on websitw what to mine.
Is this good idea?
I personally think it's impossible right now to predict how the market is going to behave over the next 5 months. It's way too variable especially with the asic about to come on line. I get the sense that a lot of folks got burned calculating their roi when doge was hot and are now dumping everything they mine just to cover costs (or their gear - craigslist is full of gpus for sale).
Yeah, that's usually the issue. People forget that this isn't a scene where the returns are stables. And usually there are diminishing returns in the crypto-currency scene. But you can consider the resale cost of hardware as part of the "break even/ROI."