First of all Lakerat, welcome! Nice to see you here.
Now, to try to answer your question.
I'm 53 and I've been shooting a 75# Blackwidow longbow for some years now. Been using nothing under 800-850 grain wooden arrows all that time too.
Todays heavy bows simply shoot heavier arrows faster and flatter. I like what Charlie said re big broadheads too.
Trajectory wise, at hunting ranges I've never found heavy arrows an issue. That's where your stumping sessions teaches you what's what. Just yesterday I was having a play at a tad over 50 yards. A couple of shots to work out the drop, and it was no real problem to put the next few arrows into or awful close to a gallon milk jug. Not hunting ranges I know, but what I think I'm trying to say is, with proper practice, knowing your arrow's trajectory becomes pretty much automatic.
Other than when I was recovering from some shoulder surgery (not bow related) that 75lb Blackwidow has been my most used bow by far. Like you I use it for everything, from targets to stumps, from bunnys to buffalo. I love it and usually shoot it pretty well.
One day, if I'm fortunate enough to have been around as long as some of the awesome older guys here, like Charlie Lamb or Ron LaClair, no doubt I'll not be as strong as I once was, and reducing my bow weight will be necessary. Until then though, I'll keep using my heavy bow.
If you like the heavier weights and can shoot them well, absolutely stick with it. Get your 75lb'er, and you cannot go wrong with a bow from Big Jim.
Best
Lex