Originally Posted by
OliverB
PS - I forgot to add that I'm booked on a "fifth night free" promo, so I assume that any paid upgrade would take that into account and deduct only the cost differential of 8 nights from our total stay.
Not to burst your bubble, but I would actually assume that you'll be charged the UG difference for all 10 nights. Your 5th night free promo covers the cost of the base room you booked. Or looked at differently, reduces the nightly rate by 20% for all 10 nights.
Either way, any upgrade or add-on would apply across all 10 nights IMO.