There is no legal restriction to the frequency that you’re able to refinance your home loan. However, each time you refinance you pay an exit fee on your existing home loan which can add up over time. Furthermore, your credit rating may suffer. When banks see that you are constantly changing your debt obligations, they will be less inclined to offer you low interest rate loans.
That being said, it’s a good idea to compare home loan products at least once every 2 years. That way you can ensure that you’re on the best product for you given your own personal and financial circumstances.