A good number of my campaigns have lasted over 1 year, usually 2-3 years.
D&D 2E, D&D 3.5E, D&D 5E, Dresden Files, FATE, and my home brew mecha game (4-5 campaigns over the last 10 years).
I normally run 2-3 games per week and I would say that 2 of them are usually long term (2+ years)