Next level sportive/GF peformance?

I’m interested in views on what the focus areas are, and perhaps training suggestions, to take sportive or Gran Fondo to the next level? I’m not after plan suggestions here but rather areas to focus on or general approaches that could help really increase speed on these 100-120 mile/5-8 hr events?

I’ve done loads of events in the last 10 years and completed lots of 100-150 mile road events, in the mountains with long climbs and rolling road courses. What I’m interested in is how to kick it up a notch - not just finishing but really being able to push on, get over climbs faster and ‘smash it’ rather than ‘slog it’. It’s not about finishing, but really performing. These aren’t races so it’s not about ‘race winning moves’ or sprints etc but I recognise that at times it is about being able to chase onto a faster group or hang on when there are some accelerations.

So, what are the ‘types’ of fitness or key performance markers or training strategies that take it up a notch once completing 100 mile events is no longer the issue? Is it more really long rides in the 70+ mile range? Perhaps its just a relentless focus on FTP increase, or extending TTE at threshold or sweetspot - 60 min, 120 or 240 min power? If you want to be hitting those gold medal standards for your age group what is it all about…and maybe how do you get there?

It would be good to get general ideas but for reference I’m 50, 75kg, 3.8w/kg, not time limited and been riding and training >10 years.

What experiences do people have and how have people achieved it?