I was thinking it might be a good thing to have a thread devoted to our lovely elderlies

What you define as 'elderly' is up to you.
It could be as young as 5/6, or 14/15, depending on your rabbit's breed and health status.

If anyone has any tips on supplements, health, husbandry and would like to share, please post

I'll kick off with using a potting tray as a low sided litter tray for those who can't hop much any more.
Something like this: