I have Smudge, an uppy-eared English self who turned 10 last September and Sora, who looks like a Havana (except a lop, so must be a cross) who is estimated to have turned 12 in December. We rescued them both in 2009 and Sora was already fully grown so I believe she is as old as they say, possibly older.
There is no secret, other than good care the only thing you can rely on is luck. Luck that they don’t get growths and cancer. Luck that any stasis episodes can be overcome. Luck that nothing else happens, and if it does, that it isn’t the end. Sora is missing part of her liver as she had a serious liver lobe torsion in 2010. Both have had multiple episodes of stasis and Smudge has also broken his toe in his lifetime.
Smudge looks and acts like a 1 year old rabbit, he has no currently known health issues. Sora is not currently in good health, her eyes are bad (completely blind) with cataracts and bulging eye tissue which has been bad for about 1.5 years but no other issues. We have an agreement with our vet that as she is not in any obvious amount of pain then we just keep plodding along and as soon as she begins to deteriorate or anything else happens (more statis etc) we are to spare her any invasive treatment and let her go. But until then she plods on, blind but still with a reasonable quality of life until she either slips away when her time comes or we intervene if anything happens. I suppose neither us or our vet realistically expected her to still be going now but she certainly is.