We have had quite a few rabbits that lived long and well - no teeth operations or big vet bills fortunately. Many were mixed breeds as all were rescues but even with Polar (who does have a chronic eye issue we treat with drops) the life they lead seems to keep them in good condition.
Firstly they are never short of grass. This is the abrasive which deals with the growing teeth and keeps them in check. We like to allow some free roaming time and we also move the runs as much as we can for fresh foraging. Grass and weeds are collected on a daily basis twice a day in winter and placed in different locations in their runaround so they need to seek them out.
Next movement, we love to see our rabbits move and wriggle, hop and jump. Polar (white lop) is less agile than Teddy at half his age. Teddy is 11 and Polar age 5 cannot move as quickly. Her poorer eyesight possibly has led her to not rushing about but I think her inbreeding has worked against her as well. To encourage them to move they need options so the interconnected run system did that and additionally whenever we visited some free roaming time.
For keeping warm and healthy I think we all can feel it is far better to be on the move. I am delighted with the speed of Teddy in his senior years, he hasn't even started to look old yet!
So keep the bunnies busy, active, munching their natural food and also I would suggest living outside. There is much to recommend it - fresh air, sounds of nature, connection with other living things.
Keep going Teddy and Polar, we are proud of you!