How long? (bonding advice)

Okayy so, I'm hoping when Thistle is all healed and calmed down a bit to start trying to bond him and Luna, however I'm worried they won't get on. He's fine because he's really laid back and never aggressive but Luna is so temperamental. One day she is in a good mood, the next a bad mood...and sometimes she doesn't mind him being near her and other days she can't STAND him!....
So I'm wandering how long I should keep going for trying to bond them before I just write it off that she won't get along with him?
If they don't bond, I'll look to get Thistle a companion but keep Luna single (even though I got him for her, but I don't think she's ever gonna change >_<)
So people who have experience may know how long I should give it before I should just accept she may be better off as a lone bun! I know some people try bonding over long periods of time, but I just have a feeling this may not work out...:/
Thank youuu