I always recommend that you line baking sheets with parchment paper, instead of simply greasing them or trying to rely on a nonstick surface. It is the best way to ensure that nothing sticks to your pan and it makes clean up very easy because it can be thrown away when you’re done. When you have to do a lot of baking – especially when you’re baking batches of cookies and nothing is left on the paper after baking – it seems like a waste to discard all that paper. Fortunately, you can actually reuse parchment paper several times before throwing it out. I wouldn’t necessarily recommend trying to re-line a cake pan with a round of parchment paper that has crumbs of a previous cake still stuck on it, but you can definitely reuse cookie paper over and over.
When I first started to use parchment paper, I often threw sheets out after baking just one batch of cookies. I was relieved – partly because I didn’t have to buy nearly as much parchment paper – when I realized that I could use it multiple times. The only time I don’t is if something really stuck onto the parchment paper (unusual, but possible) and I don’t want it to burn on another trip to the oven, or if I’ve baked something with a really strong flavor (mint or orange) and don’t want the scent to be on the next batch of cookies.
Most parchment paper is oven safe to about 425-450F. At temperatures higher than that, or if you are baking something at that high of a temperature for an extended period of time, the paper is going to start to turn a deep brown around the exposed edges and it can even start to smoke a bit. If you need to put something in the oven at 450F, that parchment paper probably isn’t going to be able to go another round. For most regular cookie baking, parchment paper can make at least a half-dozen trips into a 350 or 375F oven. After a while, the paper will still begin to turn a very light brown around the corners, but it will hold up very well for several batches of dough. You can even save the paper with the baking pans and use the same sheets another day.