i cant speak for other people but i can speak for myself. anything that i would have bought with fiat anyway that can be bought with bitcoin instead, I buy with bitcoin instead. since i do believe that the price will continue to go up, i buy enough bitcoins to offset the purchases i make with it. So in the end i have no fewer bitcoins than i would if i hadn't spent them.
Perhaps I'm missing some key info, but say I paid 1 Bitcoin yesterday for a laptop worth $725. Today I take funds out of my bank, which costs me $15 in fees, and then right now I'd have to pay $790 to get my coin back.
Well, but in 1 day interval anything can happen, you could buy back your coin at $650 as well. Only in the long term the price rise, not in particular day/week/month. About bank fees, best is move USD you dont need (there are still payments/product you can not buy with BTC) to BTC only once per month