Refinancing a Variable Rate Closed Mortgage

[Mark B.]

I bought my first rental property 18 months ago on a 25 year amortization, 5 year term variable rate closed mortgage. I made a 20% downpayment and then a 20% lump sum extra payment against the principal after the first year. At the 2  year mark, I plan to make another 20% lump sum payment. 

At that point, the mortgage will be cut down significantly and refinancing to decrease the monthly payment and increase monthly cashflow will allow me more freedom to expand and purchase another property(and so on, hopefully). 

Has anyone refinanced a variable rate mortgage before the term has expired? Also, if anyone can shed some insight on what type of fees or hassles I will run into along the way if I choose to go ahead with this plan.