Hey @user-removed, welcome to the Spotify Community!
All you need to do is get in contact with Spotify support and they can help ensure you get your full subscription time, even if you change accounts. They should be able to transfer it over for you! The easiest way to contact them is by messaging SpotifyCares on Facebook or Twitter. You can also use the online contact form on this website if you would prefer to communicate by email. They usually respond within 48 hours.
Please let me know if there's anything I can help clarify! Happy listening 🙂