I’m 63 and both my bikes the bars are about an inch and a half above the seat when dropper is up.
But to start with it is totally personal preference. The concept is for going down steep hills higher is usually better. The caveat is that they still need to be low enough so that you are not stopped from leaning forward far enough to clear steep uphills.
Personally I would like to run my bars even higher, but where they are at times doing quick sharp ups, I touch the bars with my body leaning forward. But I figure they are about right as I usually only realize that I had hit the bars when I notice I have knocked my odometer of its mount again.