Hello Courageous, Great question! Botox and other current neuromodulators are NOT known to wear off faster for first time users. Although rare, some people can develop a tolerance for botox, and have a shorter duration of effect with repeat treatments. Facial expressions shouldn't impact the duration of your treatment. The medication works on the nerves that innervate our facial muscles. Botox blocks the nerves from sending signals to the muscle that tell them to contract. Some people are fast metabolizers and will break down the Botox quicker than others, but for most people, the expected duration of effect is anywhere from 2-6 months depending on the product used and the dosing. Hope this answer was helpful! All the best,Dr G Dominick Gadaleta, MDDG Facial Plastic SurgeryPalo Alto, CA