So i think there's a standard suggestion that rabbits should be wormed every 3 months
However, the "worming" is mainly done as a preventative to E Cuniculi, and not the actual worms.
Worms aren't that common in bunnies and if you keep an eye on their poops, you will see the worms if there are any and know to worm them
EC is a parasite which i think over 50% of bunnies have been exposed to, but it generally only has symptoms if the bunny is stressed or has a lower immune system due to other illness/stress. If there are symptoms, they're really nasty head tilt type stuff that you'd really want your bunny to avoid. However, there's a risk of building up immunity to the worming medicine if it's used too much so that if the bunny did get EC, it would be less effective, and also a view that worming for 7-9 days is pretty ineffective and it should be 28 days if the bunny exhibits symptoms of EC.
So there's another school of thought that says even if your bunny does come into contact with EC, it will be ok unless it's stressed/ill, so if you worm them when they're stressed/ill e.g. bonding or boarding or moving house then it will prevent EC flaring up.
So there isn't any conclusive advice really. But I'm probably going to give my two wormer every time they come home from boarding in case the boarding was stressful (approx 2x per year)