I unstring my selfbows after I shoot, but my laminated bows stay strung unless I need to unstring them to put them in a case for travelling.
Fiberglass doesn't take a set, and that's what takes the stress on a laminated bow. One recurve I use for bowfishing may stay strung for months, if not a year or more at a time. I've had it for....10 years or so, as best I can recall, and according to my digital scale it hasn't lost anything. Been shooting the same longbow for well over 10 years, and last time I checked it hadn't lost anything.
The down side is if your string were to fail (heard of one instance where a mouse liked the string wax), it could cause a problem.
As long as you know how to properly string/unstring, I see nothing wrong with unstringing if that's what you rather do--but as far as I can tell, it's not a requirement as long as the bow is stored properly.
Chad