Xbox Game Pass Ultimate memberships are limited to 36 months.

If you're already an Xbox Live Gold, EA Play or Xbox Game Pass member (Console or PC), any days remaining in your membership(s) will be converted to Xbox Game Pass Ultimate at a conversion ratio when you redeem the 24-month Xbox Game Pass Ultimate membership, and will be added to your Xbox Game Pass Ultimate membership up to a maximum of 36 months. You will be unable to redeem with more than 12 prepaid months of Xbox Game Pass Ultimate because an account can only have a maximum of 36 months at any time. If your prepaid balance is more than 12 months, please wait until your existing membership has a prepaid balance that is less than 12 months before redeeming the 24-month Ultimate membership through Xbox All Access. If you’re already an Xbox Game Pass Ultimate member with a prepaid balance of less than 12 months, your current Ultimate time will stack with the 24 months of Ultimate that is included with Xbox All Access.

Yes! And there's no need to wait for your current membership to expire.

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