Should I try to pay investment properties mortgage early and how?

[Juan Del Arco]

I have few rental properties and all of them have a mortgage. The idea so far is to pay them all off before I retire, so I have been using the cash flow to make extra payments, but I am not so sure that this the right approach.

First, should I really need to try to pay the mortgages early, or maybe just use the cash flow to buy me nice things right now?

And if paying early make sense, which of these options is the best way to accomplish it:

a) use cash flow on each property to make little extra payments on their own mortgage (current)
b) use all properties cash flow to make a big extra payment on the one with more or less equity
c) use all properties cash flow to make a big extra payment on the one with the higher interest rate

Thank you