I have had offers from 3 days before to about 4 weeks. Most have come in the 8-21 day window. Have received offered for every category above inside in the past. Best was Pinnacle offer- and we took it. Same cruise also paid for upsell for my brother who was cruising with us and moved him from OV to SS (felt a little guilty us moving to pinnacle and him in OV or maybe he was in verandah- its been awhile & I cant recall...
Most recent was 16 days out. When I called only options were FOV and Vista Suites. only 3 Vista Upsells were available. He told me I had lots of choice for stateroom cabin because none of the guarantees had been assigned yet. The ship was still selling every category except pinnacle- Inside, IV, Balcony, Vista < SS, Neptune. (but some categories within a category were sold out- ie Vistas were avail but no Aft Vistas). I picked a cabin from about 25 options. Then the following day changed my mind about which cabin I wanted- so I called and changed. I noticed 2 days later (13 days out) that guarantees had been assigned. All categories except I, OV and Obstructed Verandah were sold out after guarantees were assigned. I doubt I would have had a complimentary upgrade from my free OV. I would have been happy in my OV but opted to change to Vista Suite (not really sure why LOL- we like the OV, love crows nest and would have been completely happy but I will love my vista suite too