Inflation over the next 10 years will be significantly higher than over the last 10. That means that your rental income will go up susbtantially, while your mortgage payment will remain fixed. My advice is to keep it as long as the cash flow is positive and the upkeep is not much of a headache.
When I was a grad student in L.A. in 1995-1997, I used to rent a 2-BD apartment for $850 in a small 12-unit building. The rent was a little below market for the area, but that was the landlady’s strategy for retaining tenants with low turnover. At some point she decided that management was too much work for her and sold the building.
I recentlty checked what those units rent for today, and they go for $1500! She should’ve held the building for longer!
In your case, there’s going to be a “hot” real estate market sometime in the next 10 or 15 years (just like we had in ’79, ’89, and ’05). You can sell it then at a really handsome profit.