Horner won the vuelta with 43 years.
Now more seriously, froome is finished, but i disagree that he was declining in 2018.
He started the giro a bit cooked to try to do the double Giro/Tour, but then the crashes during the Giro didn’t help. By the end of the Giro, fortunately he recovered from the crashes.
In the Tour 2019, he did podium, and he was cooked because of the fourth consecutive GT he did(tour 2017, vuelta 2017, giro 2018, tour 2018).
In 2019 during May, he was doing his best numbers ever, Brailsford and Froome had confirmed that. Unfortunately the crash prevented him from winning the fifth Tour de France.
It's was a shame the crash, because in my opinion he could had won 6 Tours de France (the four he won + Tour 2012, Tour 2019). He could had won so easily the Tour 2012.
Without the crash in 2019, i don't think he could beat Pogacar in 2020 and 2021, certainly he could not beat Vingegaard in 2022 and 2023, but like i said, i think he would had won the Tour 2019.