How long before a refinance actually pays for itself.

Shorter than the time you plan to stay, with room to spare. If break-even lands at 28 months and you expect to sell in three years, the refinance is technically positive and practically pointless. Under two years is comfortable for most people; beyond four, the decision usually rests on something other than the rate.

It can, and this is the part lenders rarely lead with. Dropping your rate while resetting the clock to thirty years can lower the monthly payment and still increase the total interest you pay over the life of the loan, because you have added years of payments back on. If the goal is total cost rather than monthly cash flow, compare a shorter new term, or keep the term and make the old payment on the new loan.

It preserves your cash, and it moves the break-even further out, because you are now paying interest on the costs of the refinance for the rest of the term. Rolling costs in is a reasonable choice when cash is tight; it is a bad one when it is simply the path of least resistance. Run it both ways before deciding.