"However, time will never run out on these sunglasses."
So you get in your DeLorean and you leave 1985 to go on an adventure in the past. Say it takes you six months to accomplish your goal (ie, nearly making out with your mom) and when you're done, you go back to your own time. Maybe you go back to the very moment you left.
But you are six months older. There's no way around it. The time machine can't adjust your age backward--if it did, it would be altering your brain at the same time, wiping out the memories of what you experienced. No matter how many rejuvenation clinics from the future you visit, you will always age along your own timeline just as certainly as Marty did throughout Back to the Future.
Poor kid aged five years in one damn weekend.
When you get to the core of it, traveling through time is pretty much a deal with the Devil. Yes, it will enable you to save John Connor and get to Muggle Studies on time, but it will shave several months to several years off your life depending on how much you abuse it. These are precious moments from your twilight years that you will never get back: one last weekend with your wife, your granddaughter's graduation and the inevitable cloning of John Candy.