With TurboTax Live you have one year from the date of the return to get help from an agent. TurboTax does not offer assistance with returns more than one year old.
Not sure what "guaranteed" service you are expecting. TurboTax and the IRS save your returns for seven years. The online "Live" experts only help with current tax years--they do not go back and review past year returns. They will help with 2023 returns now; they will not help with seven years of back returns.
I found this in the guarantee. It will cover 2023 for 7 years going forward. Not back 7 years of returns.
https://turbotax.intuit.com/corp/license/online/
The TurboTax Accurate Calculation Guarantee is for the lifetime of your 2023 individual tax return, which Intuit defines as seven (7) years from the date you filed it using TurboTax Online. The Guarantee applies only to individual returns filed using TurboTax (excluding business returns), and only if filed with the IRS or, in the case of state returns, the relevant state tax authority, all subject to the terms below: