I know this is not a popular concept, but truly what is the reasoning behind thinking a few possesions holds a lounge chair that you are not sitting in.
Why is a pool lounge chair any different from say a spot to watch a parade, next time you want a certain spot to view Spectromagic, leave one of your shoes on that spot and see how that works out.
Or do you have a favorite place to sit at Cape May Cafe, be sure to go early and put your sunglasses on that chair.
I mean seriously folks if you ain't in the chair, it ain't yours.
The only saving of a chair is when you are using the chair, and get up for a few minutes to use the restroom or a quick in and out of the pool to get wet. Then you leave all your belongings on said chair and you are gone only minutes.
Anything more than that is totally unreasonable.
I agree Sammie. It's simple and if everyone followed it there would not be a chair shortage. Enjoy it and move on.

The sad part is that not everyone will follow the same rule so the sentiment is moot and people will continue to save chairs.
For the record, I do not recognize a shoe, flop, or magazine as a placeholder. I give towels 30 minutes and then I ask a lifeguard for assistance.