4-5 good years before age 30 is the definition of sustained success in 2024.
Having a 20% above average ERA for your non-"prolonged" career, including 7 of 10 + 100 era+ seasons is getting all of the controlling years of a $15m/yr SP (2nd or 3rd rotation slot) for minimum and arbitration prices.
For the Sox that means getting all of their good and cheap years before they become a free agent or get traded. He will most likely be long gone before your theoretical collapse.
While you always hope for Hall of famers, if you get that out of Thorpe, that's a win for the Sox.