So , this sounds like you should always sell calls on your long term holdings. Doesn't it?
I think you may want to look up how volatility works, etc. These kind of banket-statements 'always do this/that' will lead you to all sorts of tiny-reward, bigger head-ache type risks.
It almost sounds too good to be true.
There is a saying about that... if it sounds too goo to be--
It's a zero-sum game. Actually, even worse because of commissions, slippage, etc.
Is there a situation when this strategy of indefinite rolling stops working and you end up losing money on your calls?
Sure, you could roll until your account blows up. When you roll, you are TAKING THE LOSS. Because you are closing your contract outs and locking in a LOSS, then re-opening another contract on the HOPE of somehow making up for those losses.
There are limits to how much you can keep pushing your losses down the road if your trades don't start winning. Even so-called professionals have blown up accounts that way. Karen-the-Super-Trader was one example. Even worse in her case, she got into legal trouble for not properly reporting those losses, yet billing the clients for the trades IIRC.