I personally do it every few months now that i know the amount of gunk that my bunny produces. For me, I personally recommend it not only because two of my rabbit savvy vets recommend it but because there have been times when I have had to clear out rock hard wax like pieces that could not have been comfortable. (also, in some cases it can clog and cause infection and/or irritation). If you check every month at least for a while you will begin to know how often your bunny may really need them checked and or cleaned.
Obviously there are different points of view on this. But that’s okay — that’s the nature of forums. What works for some, may not work for others. We all have to do what we each feel is best. I can say though, that in all the years of this forum, my personal experience and listening to other’s experiences, I have yet to find a member/person who has had a bunny with infected anal glands (though my vet has had experience with that). However, we have had members note that their bunny was extra pungent and cleaning out the anal glands seemed to help in some cases.)
I personally take a precautionary route and follow my vets advice regardless. (and obviously this site’s monthly maintenance section recommends that as well).