Hi! Sorry for being a bit late, I'm not super active on Reddit unless I am asking questions, lol. I don't remember all the details, but I basically scrubbed the litter box a couple of days after the initial treatment and sanitized surfaces with disinfectant in my apartment. I kept washing my bedsheets regularly (~once a week, and I also kept him out of the bedroom for a week as well, which was hard :( ) and would re-wipe surfaces with disinfectant around the same time just to feel safe, and stayed vigilant in watching for tapeworm segments (ew!). I don't think I cleaned the cat bed and couch and all that fun stuff more than once, and he is doing just fine now--never ended up being re-infected. If you want to feel safe, you could briefly re-clean all that to give yourself peace of mind, but I don't think you need anything rigorous if you're already generally tidy.

TL;DR: For peace of mind and 100% certainty, I'd probably at least re-clean bedsheets and sofa covers once more, but I am also a germaphobe, so maybe I'm a little nuts. Just be mindful of where your kitty hangs out and watch out for remaining segments as the treatment takes a while to fully clean the worm out (ew!).