Scripts you save stay in Script Studio, so a script you wrote for one listing can be opened, edited, and used again.
The fastest way to reuse one is to open the saved script, change the details that are specific to the new property, and save it as the new version. Most listing copy is structure plus specifics, and the structure is the part worth keeping.
A script attached to a property opens from that property's workspace as well, which is usually the quicker route when you are already working on a listing.
Script Studio does not use credits. Write and rewrite as much as you like.