The thing is, each time I have enough Bitcoin, I turn around and convert it to dollars to pay some of my credit card bill (not because of the miners, just need the cash to pay it) so I'm not hanging on to BTC long enough but at the price I'm getting, with BTC ~ $450-$470 USD, the extra couple of hundred that has gone to the credit card makes a big difference.
Nothing wrong with this strategy, as long as you're aware the income stream is steadily declining.
Some miners mine and hold BTC, some miners mine and sell BTC, some miners mine and reinvest BTC into more gear.
Smart miners do a little of all of the above.
