Apparrently Rob Singer has read this thread and sent me an email regarding his thoughts on the matter. Since Rob does check in at multiple hotels many times during the year to take advantage of his FSP, he is probably well versed on the subject. Here's what he has to say:
" Bob: As someone who has ALWAYS checked into at least 4 and as many as 9 hotels on the same day for years just to get the freeplay or gifts/freebies while only staying & playing at one property the whole time (and I used to go to Nevada every week in the 1st half of the 2000's, and several times a month since) here's the truth about what one needs to do and what might happen, and why:
Myth: If you check into a hotel for the freeplay and do not play or stay there, your offers will stop coming. That's inexperienced BS talking. You've played at the property before and they'll ALL keep on sending you offers for at least 6 months until you convince the marketing dept. computer that you are no longer interested in anything but raping them. And still, you will get another offer in a year or more just in case they can entice you to being a loyal customer once again.
--You must call your credit card co. (in my case AMEX) and alert them of multiple checkins and they'll so note it on your account so you won'y have your card frozen.
--Next, regardless how many nights you're checking in for, you must go to the room and mess the bed/use the bathroom. Why do this if you're only checked in for one night? Because you're playing the comp game, and there's a chance your assigned host will find out that you really didn't stay there. And when he/she checks your card and find you didn't even play beyond the freeplay they could override the offers being systematically spit out by the marketing computers.
--If you're checked in for more than one night you HAVE to mess the room a little as well as put up the Do Not Disturb sign. Why? Because if housekeeping goes in and finds no luggage they WILL call the checkout into the front desk, and at most or all of the nice properties the small print (which most people don't read because their hands are sweating as they await their gambling fix) clearly states that should you stay less nights than your agreed-to stay, one night at the going rate, which is expensive, will be charged to your credit card. This will also mess up your offers if your host finds out about it.
--I always write down the hotel, the room number, the tel. number, and the check out date for each comp checkin. On checkout day I call them and simply say "I had to rush to the airport and didn't even have time to use the TV to check out, so I'm doing it over the phone now."
If you do it right it's really simple, in most instances no one who counts cares because no one who counts knows, and out of over a thousand comped checkins I've only had two issues that I fixed by being smarter than the person who got on my case."