Should I pay off the mortgage sooner?

[Sergio Martinez]

Pardon me if this sounds like a beginner's question. I have an investment property with 2 tenants paying off the monthly mortgage (30 year fix @ 4.25%) leaving me with a little less than a 1k a month. I’m debating whether I should really dedicate all my funds in paying off the mortgage in 10 years or should I instead use that money for the down payment to another property which is one of my goals. I really enjoy living debt free. Any advice?