Does SPG require physical check-out at front desk? If no physical checkout required, you could check your bags w/ the bellman & head to the exec lounge slightly before 4pm to hang out - ie, if you're there before your card key expires & are reading/working on the laptop, etc, before evening drinkies odds are you won't get asked to verify your room #, especially if they've seen you in the lounge before. Of course if you have to leave to use the bathroom then you won't be able to get back in as your card key will have expired.

I'd ask & hope for the best. It probably depends on the property & how full/what else is going on. As often1 notes, don't count on it but be pleased if you get it. Or potentially try the above w/ the caveat it might work/might not work but even if it works may not work as long as you need it to do so.

Cheers.