I've sold at $38 all the way up to around $58 or slightly better but I didn't do astoundingly well in terms of catching the highs. I am satisfied though.
Selling some this week was very good as it enabled my covering IRA liquidity requirements while not sacrificing any NGL holdings. Got about $40 which pleases me. Still holding a few but worth only a grand or so.
As a rule, DK will rise in early morning and then fall back. Sometimes it will resume an upward bent but typically falls back into the close. You're definitely correct about the wide spreads. A day trader could make easy money here and have fun playing the odds. That's what I did for years, using stocks like DK as the bait.