Hello.
Normally, I run my MBPr under high loads (i.e., gaming, VMWare for work, Keynote lectures, etc.), and the display gets left open fairly often, too. After about a year or so since I got it, the hinge sometimes gets stiff when I close it, as if it needs oil.
Anecdotally, my last two Mac notebooks developed the same issue after about a year, never developed into anything much beyond a simple stiff hinge, a 12" PB and a 2010 15" MBP; neither had any major failure as a result of the hinge, thankfully.
When my current Mid-2015 MBPr developed a stiff hinge, I finally took it to the Genius Bar a few weeks ago, and the MG said it is considered "normal" for some stiffness/rigidity in the hinge under extreme temperatures (i.e., cold, hot) which is indeed the case.
Normally, I just run the hinge fully open/closed a few times to work it out every few weeks but otherwise it runs like a champ.
You can always take it to the Apple Store and have them look at it if you're concerned.