I trade SPX weekly calendars every week quite successfully. It is key to adjust them early when price approaches breakevens, either with a long option to reduce Deltas to zero or turning it into a double calendar. Don't try to ride them all the way to expiration, get a 10% profit and exit.
So you buy the calendar when? Monday? Previous Friday? Then you buy long OTM put or call to pull delta towards zero when the underlying moves to breakeven?