.
Just checking - are you reading your loan documents currently? An ARM, short for "adjustable rate mortgage". My experience with 5/25 ARM's - the interest is a fix low rate for the first five years. After the fifth year the loan becomes adjustable as much as 2% per year. The most popular reason for getting an ARM compared to a fixed rate mortgage. People are expecting to move before the rate changes.
Understand if you have a jumbo loan, a small difference in the interest rate, can have a big impact how much you will pay. Having a smaller conventional loan, if there is not a big difference with the interest rate, it can result in a small impact on what you pay.
If the interest rate is indeed fixed at 5.5% after your loan recasts. By refinancing what you would pay in closing costs added to your loan, any savings with a smaller interest rate, will be eaten up by the lost equity.
Only two years into your loan you have to look at the amortization of your mortgage. You're paying almost all interest with very little going to your principle. The first five years on mortgages, more goes to interest than what is paid to your loan balance. Right now you've paid very little to your principle.
Recommend you stay where you are for now- in three years as you get closer to your recast date, then start comparing your options. Getting into a new loan, you're starting all over again with a larger balance to me doesn't seem like a wise move....
Think about this - send more then to required payment now. At your current rate of 2.99% sending extra, your money is stronger because you are being charged a lower rate and less interest is added to your loan. When the rate goes up sending extra, your money is weaker because interest is charged adding to the loan.
Good Luck.
..