I booked the flights well ahead of time, just when I found cheapish availability. Then I waited until within 4 months of the flying date to make the status match request - this was on an existing TK account though I'd never used it. The only issue I had was that the name on the account didn't include middle name which prevented me from adding the flights initially, but customer services were very good.
The match process itself is really fast. Was done overnight I think. I now have status until June 2026 following the flights.