Had 5 free night certs expiring soon, so I booked them as separate reservations for the same hotel just to see what would happen.
At check-in, I explained the situation. They couldn’t link the upgrades, but the front desk kept me in the same room all 5 nights just had to rekey my card each day. Got the usual daily “check in / check out” emails, but I ignored them and it was fine.
Overall, smooth process and great staff. Just expect a little extra front-desk time if you try this.