summary: if you're on an annual plan and upgrade to all access, your subscription switches to monthly billing and the time you've already paid for doesn't disappear. it's turned into an account credit that's applied to your all access charges. here's exactly how it works, so the numbers make sense.
what happens when you upgrade
upgrading from an annual plan (for example, an annual essential plan) to all access does two things at once:
your subscription converts from annual to monthly billing on all access.
the time remaining on your annual plan is converted into an account credit based on what you'd already paid for those unused months.
so you don't lose the value of your annual plan, and you're not paying twice. the prepaid time follows you as a credit.
where the credit goes
the credit is applied against your all access subscription. it covers your first all access charge, and whatever is left rolls forward to cover your next monthly renewals until the credit runs out. once it's used up, you're billed the normal monthly all access rate from there.
a worked example
say you were a few months into an annual essential plan and still had several months of prepaid time left. when you upgrade to all access ($299/mo), that remaining time becomes a credit on your account.
for example, if your remaining credit worked out to around $600, it would cover roughly your first two monthly all access charges, and you'd start being billed the normal $299/mo only after the credit is exhausted. the exact figure depends on how much annual time you had left at the moment you upgraded.
what the "you'll lose access in X days" message means
when you make a plan change you may see a message that access ends in a number of days. that's referring to your billing cycle date, not your prepaid value. your credit is safe on your account and is applied to the new plan. if anything about your balance looks off after upgrading, reach out and the billing team will walk through your specific account.
when you'll be charged again
your next charge is the monthly all access rate, on your monthly renewal date, once your credit has been fully applied. until then, renewals are covered by the credit and you won't see a new charge.