I made it four times in the Banquet Hall fight. There's several ways it could work though.
1) Sword has Returning property permanently.
2) Sword has Returning x/day.
3) While in Green Fire mode, sword has Returning.
4) While in Green Fire mode, sword has Returning (x/day)
5) While in Green Fire mode, sword has Returning. Using returning reduces the duration of GFM by one round.
Or ki points. Or psionic power points. Or essentia.
Really there's a lot of variables that I doubt Rich will specify, as doing so means nitpickers be nitpickin'.