Since fillers expand the lips, does this create more wrinkles and less elasticity if you stop the injections?

While it is not unreasonable to think this is a possibility, once the filler has dissolved (typically after 4-6 months in the lips) your lips will return to their normal pre-injection size and shape. Even though the filler does expand your lips, it is using such a small amount of product to do so that it would not have any permanent effect on your lips.

Thank you for your question.  It's important to remember that when we talk about syringes of filler, we're actually discussing very small volumes of product.  Most of the commonly used lip fillers (Juvederm, Restylane, Restylane Silk) are packaged in 1cc syringes - to put this in perspective, it would take 15 syringes to equal 1 tablespoon of product.  The skin in our lips has very high elasticity, and the stretching of the skin from a regular dose of lip fillers should have no permanent impact or create any laxity once the filler has been metabolized by your body. 
I would recommend seeing an experienced cosmetic dermatologist or plastic surgeon to discuss your concerns and to determine the best treatment plan for you.  Best of luck!