It doesn't sound so very hard to me. All the actual graft is done by others.
She's turned out for thousands of ceremonies
Travel arrangements, itinerary all organised by someone else. Research conducted and speeches written for her. Someone on hand at all times to tell her what to do, where to go and what to say.
always looked and presented herself immaculately, (who'd want to have to look their party best 24/7)
Again, someone else to choose, fit and look after her clothes. A bath run for her every morning by her lady in waiting. Hair/styling sorted by someone else.
She's travelled (allbeit in luxury) without her husband, or her children, to places all over the world, for more than half a century, representing this country and fostering good relationships
As you say, in luxury, being exposed to people, places, things the rest of us can hardly dream of. A team of advisors on hand at all times to tell her what to do and what to say.
She has a ton of paperwork on her desk, which she deals with every single day
Assisted by a large, dedicated team of secretaries and admin people.
she puts duty before self at all times!
I think I'd find that very easy in the circumstances. The rewards are substantial.