When does refinancing make sense?
The two big questions when refinancing are "how much will I save each month?" and "how long until I break even on the closing costs?". The break-even point is simply your closing costs divided by your monthly savings.
As a rule of thumb, if you plan to stay in the home longer than the break-even point, refinancing tends to be worth it. If you might sell or move sooner, the upfront costs likely outweigh the savings.
Don't forget to factor in the lifetime interest difference — extending a 25-year remaining loan back out to a fresh 30-year term can lower your monthly payment but increase your total lifetime interest, even at a lower rate.