For me I sell all the Altcoins that I mine basically for bitcoins because it's gaining value than all cryptocurrencies and it's also part of my dream to raise at least a total 21 BTC and save for the future.
If you look at the alt coin market all the coins are having a good rally and if you are mining and were holding some coins then the chances of making a 100% return is very much possible with the kind of rally every coin had in recent months.