Well the Queens schedule is something like Morning = Red Boxes/Corrsspondance
Early Afternoon = Receiving Ambassadors etc
Afternoon Proper = Engagement
That's most days of the year bar weekends. So that's a busy schedule.
Charles has a busy one too, as he has boxes too and does more travelling with it.
I suspect Edward has quite a lot of DofE meetings but we never see all that. He and Sophie travel a hell of a lot to the Commonwealth. I imagine their kids have been at boarding school for years at this point which makes it easier.
Andrew busies himself in trade. We have no idea what that entails but it is his niche and it may be more important than we give him credit for.
Honestly I can account for most of the older ones. It may not be a 9-5 but you can see there's enough to do each week.
I have absolutely no idea what William and Harry do on a weekly basis. Harry at least did a tour and then went to Africa (massively underreported as he was alone). And they're doing a tour next year.
But outside that, I'm honestly not sure how they fill their time.