I think whether you want to keep and divide the old crowns or use the new ones depends on whether the original crowns were a modern variety from a crown or grown from seed themselves. If they are all seed grown, then I feel it won't matter and just select the crowns that you like the look of most - if you can remember for example which gave the best spears. I've certainly heard that asparagus can remain in the same bed for 20 years or so - 100 is outstanding! Your family must be doing something right Leora!
I struggle a little bit with asparagus although I have some in my old polytunnel space which I am intending to move, so it is reassuring that it will divide. I think I probably don't feed mine enough and it definitely seems to appreciate the extra warmth from the polytunnel in the summer here. I'm hoping I can get it to grow outside on some of my mini hugel beds - better drainage and selected sunny positions perhaps.
My suggestion is to divide when you think it needs it - whether that is 3 years. 10 years or never

If the crowns starts to lose vigour, are crowded, and a good dressing of rich stuff doesn't perk them up, then division seems like a good plan.