I really like the way that both answers given so far (with délester and acquitter) make the speaker sound (to me, at least) like s/he’s actually doing the other person a favor by offering to help lighten/relieve the heavy moral burden that the ever-growing backlog of promised, yet undelivered favors must certainly be causing!
Unfortunately I can’t find many examples of the following suggestion (which probably means that the structure is incorrect or at least not idiomatic), but with that cool notion/strategy of “appearing to be offering to help relieve a burden” in mind, maybe you could consider attempting to highlight further your playfulness by playing a bit off of the word “charges” with:
“En parlant des charges de revanche, peut-être qu'il serait grand
temps que tu t’en décharges un peu [sur moi]!”
See the following usage example from what appears to be a translation of a Hachette/Harlequin romance novel, via GoogleBooks:
“Tu portes un lourd fardeau, Dr. Riley. Il est peut-être temps que
tu t’en décharges un peu sur
quelqu’un.”
Cf : this similarly constructed example
(but using “par” instead of “sur”) from Volume 3 of the Sermons du pere [Louis] Bourdaloue, likewise via GoogleBooks:
Car vous ne ressentez pas le joug du baptême, ou parce que Dieu vous
donne des forces pour le porter, ou parce que vous vous en déchargez
par une lâche infidélité.