Unless you are overexposed don't look at in-play bets as "hedging a bet that looks good" or "saving a bet that looks bad".

A bet made live should be looked at on it's own merits, does it have value in it's own right?

If you are looking to trade in-play set yourself an exposure limit and avoid temptation to go over that even if the book (or exchange) is still throwing numbers which appear to be off.