Hey Nathan,
Thanks for reaching out. One license should be fine but definitely reach out again if you ever find specific issues!
Once license should be “fine” because you shouldn’t even need to enter the key into all environments – basically, the license key does not affect the functionality of the plugin in any way.
A license key simply signs up a domain name for updates and support.
So, many people with similar setups as yourself will use the license key just on development – when an update is available, then, they update and development and then just push the changes up to production and/or staging…
Just an example. But again, if there are any specific issues or you need one extra environment to be licensed we can help out 🙂
Let me know if this information helps!
– George