That is nice to know.
It can be expected to have a river otter live twenty years. Does a little good luck, a good environment and good care (maybe good genes, too), but it is very important to know your otter and be able to maintain health and be able to effectively treat any ailment.
An otter with a meaningful life and plenty of attention can live a long time.
My kids' veterinarian was a witness to how I was able to give Benjamin his prescription meds- open mouth on "command" (like a human baby) and I would squirt the stuff in.
From the age of just before his eighteenth birthday until his passing 2 1/2 years later.