Please note, this is speculation, but serves to clarify how this works.
Parties that store encrypted VPN traffic are often state actors with many technical capabilities. These actors won't do that for a single home user using a VPN, but a commercial party offering these services at large to certain clients may be in their sights.
When network traffic is indeed stored, and that can be at many different places in the network path (often via Internet exchanges where many parties peer data), you will not hear anything about it. Depending on how Epik has configured OpenVPN (q=perfect forward secrecy, etc) historical traffic can be decrypted. It is concerning that Epik kept all these historical OpenVPN config files on their servers/backups. Since they did this, I have a lot more questions about how they have properly configured all their super-secure services.