You do not need to put it into “Beta Test” and renew it every 90 days to have multiple accounts use your skill, I have had three different user accounts linked and operational for over a year by adding them as devs on the account where I have my HA-related skills. It might be possible to give them one of the lower tiers of user permissions, so they can’t log in accidentally and muck something up. But, since I only use the account for Haaska and Actionable Notifications I didn’t bother testing those.
This is done through: https://developer.amazon.com/settings/console/userpermissions/detail.html
For some unknown reason it can take up to 24 hours for the skill to become available to them in their Alexa app once they complete the process, so don’t get anxious if it’s not there immediately.
Also, be forewarned that using multiple accounts in one household can cause some issues. For me the most annoying has been that it interferes with using the last_called attribute in automations and scripts, because each account has a device where last_called is “true”. You can work around this by comparing last_called_timestamps, but it requires some experimentation with entity updates and delay lengths in the scripts to be reliable.