Wish I'd read that this morning. Got the ??? for several hours, then took the sensor off, after only 8 days.
I've been averaging 15 days, on my abdomen. Tried my thinnish arm once and it was uncomfortable as heck. Took it off after one night and haven't had the nerve (excuse the pun) to try again, though it would be more convenient because it frees up space for my Omnipods.