Underwhelmed This Trip
I just stayed a few days ago . Can't help you with the possibility of a late checkout other than to say they typically are real sticklers on doing things by the rules. As a Spire Ambassador they offered 4 p.m. to me but we left at 1 p.m. I had actually booked a room at the Venetian. Upon arrival front desk mentioned pool construction and noise, so suggested a room at Palazzo instead. Fine, both hotels are nearly the same IMO. Standard suites are all I need as well--simply wanted a view not of the mountains and parking garage like last time. Clerk repeated many times about finding a 1 tier upgrade for me. Based on the very low rate, I assume occupancy was low.
Our assigned Palazzo room had a view of the Venetian pool construction site, rooftop with HVAC units a few floors below, and the McCarren airstrip. Too much of a hassle to treek back to front desk, stand in line, and ask for something better. Also, housekeeping cleanliness issues with the shower. The standard suite itself was, as always, very nice. Just be aware everyone from both hotels will be using the Palazzo pools. No mention of Venetian pools being closed on their website, booking confirmation, or email offering an upgrade for extra $. Based on the excellent view of the work in progress on the Venetian pools from our room, it looks like a major project.
I hear you on the Ambassador renewal, but every year I end up going for it at the last minute.