I like your analogy of gym membership to other VPN providers!

If I may use analogy to describe UpVPN - its like buying Milk - you pay upfront you bring it home consume it and go to grocery store and buy more.

UpVPN is an option in spectrum of VPN providers. Only you can determine based on your usage if this option makes sense for you.

What UpVPN does provide (unlimited devices without subscription and your never expiring balance stays if you come back months later) other providers do not. And vice-versa UpVPN for its pricing model does not provide unlimited usage.