Prof G has written an article about this recurring question. The TL;DR version is do it asap as there is no value in waiting. The B cells are fully suppressed. Personally speaking: when I came off ocrelizumab (Ocrevus) it took 72 weeks to get a hint of a B cell after 5 full infusions. Full article is here: https://gavingiovannoni.substack.com/p/q-and-a-52-timing-of-your-annual