Interest rates can rise and fall sharply over a short time, or remain almost static for extended periods. If you locked in your mortgage at an interest rate that is 2% or more than what the current market is offering, it's a good idea to consider refinancing.
Remember though, that you will pay a penalty, which can be based on the balance of your borrowing term, and also influenced by when your loan was taken out, or last renewed. This has to be weighed against the benefits over the term of the mortgage. Basic calculations show that for the average mortgage borrower, it takes three years to recoup the cost of refinancing, even with a lower interest rate.
So, consider if this is the house you will always live in. If you have no plans to move, then taking advantage of a better rate than what you are paying, makes sense.