No. Credits never expire, and there is no monthly reset to work around.
That suits how most people actually shop. You might use five credits comparing coats in November and nothing again until spring, and there is no penalty for that gap. Nothing is lost by buying a package and using it slowly.
It also means there is no reason to rush a decision to avoid wasting a balance, which is the pressure that makes subscription credit systems frustrating.
If you are unsure how many you need, start with the smallest package and add more later. The per-credit price improves at higher tiers, but nothing is lost by starting small and topping up once you know your own usage.