While testosterone has its subjective benefits, it also has its risks: it suppresses the immune system, increases aggression, and generally shortens the lifespan of the individual producing it. For this reason alone, your male bunny may life a longer, more peaceful life if he is neutered.
How old is he now? In all honesty, I would consider getting him neutered in that case.
He will be much happier without his hormones troubling him and, the longer you let him carry on with the humping, the more likely it is to become a learned behaviour/habit as well (meaning if you got him neutered later on down the line, the humping might not necessarily stop then).
I have been putting it off. Worry that it will change his personality I do feel that I should get it done now though, as he will be four next week.
I assumed he was much younger as the humping had just started.
Alfie is the only neutered boy I've ever had but I think neutering usually has positive effects on personality, not bad ones.
Could be the time of year?
Yes I think it's definately the time of year - he is always 'friskier' around spring time. We've had Bramble for two years now, he previously belonged to my OH' Brother.
I think the reason he has only just started 'humping' is because he didn't have anything to hump before! I brought him a little stuffed rabbit just before Christmas, and now we are seeing some 'action'!
I really think I should get him done now. Everything tells me it is the right thing to do, just worries me.