I always have an exit strategy in mind -- but here's the base of it:
If AAPL moves more than 35 pts in the first week AND the trade is less than 30% down -- I look to roll, diagnol, or double calendar
If AAPL moves more than 35 pts in the first week AND the trade is down more than 30% -- exit
In week two, again 35 pts
In week three, 45 points
In week four 55 points
Though once getting to week three or four, depending on the credits the previous weeks, your options open because a large part of the trade should be paid for.
You can't just use an absolute get out of the trade if AAPL moves up/down by more than a certain point -- primarily because if it moves that much, volatility is almost certainly higher, which increases the premiums and you might be able to stay in and still make money.