My rabbits don't really get fleas. I think I saw one on Dill once (when I had three cats), but they jump on and jump off for the most part. They're not too fond of rabbits. Although a port in any storm, I guess.
And they stay in the grass until fall, here. September and October seem to be flea months. (Or at least they certainly were when I had dogs). I remember past years when they were really a problem, but not lately, I think we're on a 'down' cycle.
Mites are a different story, but most rabbits will have fur mites, they only tend to get a hold and make themselves known when the rabbit is stressed (physically and mentally).
Ear mites will need treatment, though. Watch out for those ones.
I'd wait for symptoms before treating them. Ivermectin, Revolution and Advantage are very safe, but somebunny somewhere can have a reaction to anything, so even if the risk is one in a thousand, don't take it unless its necessary.
Hope this helps!
(And we still should have a BC bunny party)
sas :bunnydance: