If your rationale is to convert to BTC immediately, then wouldn't you be better off mining in one of the multipools or middlecoin?
What I do is I mine based on coinwarz and I hold a portion of coins that I actually believe. Those I don't believe in get traded at the end of the day to BTC or LTC.
TBH, there is no way to speculate whether this is more profitable than converting immediately since who knows what's going to happen to these altcoins a couple of weeks from now. The only thing that seems to be constantly profitable for me is mining hyped up coins then day it drops.