when option price up 50%, buy it back

then roll up to a new one with higher price, make sure you always roll up with credit, rather than debt, and use time-value as your friend.  But if not doable, roll with small debit is fine too. Basically when you buy intrinsic value while selling time value, you won't be too wrong.  Aslo, after rolling, you may sell put or put spread more aggressively than you would usually do.