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Join Date: Sep 2009
Location: Minneapolis: DL DM charter 2.3MM
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Posts: 102,617
Unless a mistake is made, back-to-back stays in the same property count as one stay.
In addition, in principle, the hotel could force you to check out and change rooms, but this would still be a single stay (and it's costly for the hotel to clean rooms between guests, so they have an incentive to avoid having you change rooms).