best advice is what has already been brought up: look at the cost to refinance, see how much you will save to do so, and calculate the break-even point (how many months will it take to have saved as much as you spent to do the refinance). If you think you'll sell or refinance before that break-even point, then don't do it.

Of course, the tricky thing there is that you don't know when or if rates will get lower. You may not know when you'll move, but you'll have a better idea on that one. However, the cheaper the refinance and the lower your interest rate will be as a result of the refinance, the better, and your break-even point may even just be a year, give or take a few months. In that case, I say to do it. If you're unsure on what break-even point is acceptable for you, look at how long your mortgages up to this point have been (I think I heard that the national average is about 7-10 years). For you, it might be 3-4 years. If in doubt, it's probably better to assume that your new mortgage will last longer, so if your mortgages usually last about 5 years, then a break-even point of 5-6 years may be acceptable. For one, it is good to note that it is linear; the closer you get to the break-even point, the less money you'll have saved/wasted. Meaning that if the break-even point is 2 years and you end up refinancing 18 months later, it's not a big deal, and although you'll have been better off not refinancing now but waiting until 18 months from now, you'll have recouped most of the money spent on the refinance. The real pain point is a break-even point of 7 years and refinancing in 2 years.

One other thing to consider is the current term and the new term. It can be hard to compare apples-to-apples if have 24 years less and are considering refinancing to a 30-year mortgage. While the monthly payments will be lower on the new 30-year mortgage, you should consider the fact that doing so will mean you'll keep paying a mortgage 6 years more than if you didn't refinance. On the other hand, there is nuance there in that money is worth more now; a $2500 mortgage will likely hurt you a lot more financially now than it will 15 years from now.