I had the same road bike for 21 years, and the same touring/commuting bike for 23. Then, between 2009 and 2012 I bought, in order, a new IGH commuting bike, a new touring bike (because the IGH bike wasn't great for long highway rides , and a new road bike. Now I'm thinking of swapping the IGH bike for a Surly Moonlander or something like it. After that I'll probably be good for another 20 years or so, by which time I'll be in my mid-70s.
Once every 22 years whether I need it or not... that's my new motto for bike acquisition.