Rental coverage generally continues for a reasonable settlement period
If your policy (or the at-fault driver's policy, in a liability claim) includes rental reimbursement or loss-of-use coverage, it typically continues for a reasonable amount of time after a total-loss decision — often described as a reasonable period to allow the claim to be settled, rather than a fixed number of days written the same way everywhere.
What actually determines the length
The real answer depends on several things at once: the specific terms of your policy (including any daily or total dollar limit), whether you're working through your own insurer or a liability claim against someone else's insurer, how quickly the settlement itself is finalized, and applicable state law around claim-handling timelines. There is no single universal deadline that applies to every claim.
What to do while you wait
Ask your claims adjuster directly how long rental coverage is expected to continue given where your claim currently stands, and get that answer in writing if you can. If the settlement is being delayed on the insurer's side, that's worth noting — it may affect how long rental coverage reasonably should continue.