I don't wait to get too close to short legs, I take profit when we are close to them, get out if we go to quickly in their direction. I took 450 usd profit from my position of May when we reached minus 2600 on NDX. The trick is to make a debit broken wing, not a credit one.
Would be a broken wind condor a better strategy? Its debit spread can be broader than one of a butterfly. Though a bit more expensive. And what you think about selling butterflies (-1 +2 -1), the price needs to go away from strike price to profit. On volatile markets it could work probably.
You can buy OTM butterflies if you want to play volatility, better Risk/Reward than short fly. +1-2+1 2XSTD away from current price
Twinsen I have started doing this primarily to the upside on the SPX tight 5 pt flies or BWB...simply because set has an upside bias anyway so If I'm short a call spread when the market goes down I'll add the long call spread to create the short fly....it has worked pretty well in this market.