Do you mean headline between being nominated and the winner? Either way, it seems winning that doesn't bode well for anybodies career at all.
2023 - Fred Again.. (2nd) > 24 headliner
2022 - Central Cee (5th) > 25 headliner
2021 - none
2020 - none
2019 - Lewis Capaldi, Sam Fender, Billie Eilish (nominated) > All 23 headliners
2018 - none
2017 - Davie (nominated) > 22 headliner
2016 - Dua Lipa (nominated) > Glasto 24
2015 - Stormzy (3rd) > 20 headliner
So it seems that the next headliners come around 4/5 years after appearing but not winning sounds of.
There has been opportunities over the years that Glastonbury could have got Biffy if they wanted them. 2014 for example, year off or not I imagine Biffy jumping at it. It was very much a time though when Glastonbury got the band before others did and you could almost guarantee a Glastonbury headliner went on to do Reading until recently times. Prince was also the reason Beyonce headlined Glastonbury 2011 instead of subbing Coldplay.
I don't think they were ever in the conversation for 2015 though and if they hadn't done it by then they weren't. They returned to sub in 2017 and chose to bump up Florence and get The Libs in on a quick in and out instead. A band who hadn't played for 4 years and then 6 years later still weren't given it and we know Simon Neil would bite the hand off for it.