Just made this decision ourselves. We are 5 years into a 15 year note at 3.1% with about $145k left to pay on it. We have a decent emergency fund (18 months of expenses not counting rental income/expenses), but wanted to hedge our bets in case of a job loss. DW and I both work, but my income accounts for around 80% of our total income, so a job loss on my end is what we're trying to hedge. I wouldn't say it's highly likely, but certainly more likely since mid February.
Worked with our local bank and was able to get into a 30 year note for the same 3.1% rate, closing costs of $1,700 broken down as follows:
$750 Bank Fees(Closing Fee, Origination Fee, Underwriting Fee)
$52 Credit Report Fee
$14.00 Flood Determination Fee
$303.00 Title Work Fee
$70.00 Tax Service Fee
$400 Appraisal Fee
$57.40 Mortgage Recording Fee
$57.40 Mortgage Release Fee
Our intent is to continue paying the same payment as before which results in the same payoff as the 15 year note (age 55), but if the shit really hits and I were to lose my job, it would cut about $740 off of our basic expenses (nearly 20% counting rental expenses, 27% excluding rental expenses). This extends our range from 18 months to over 2 years (up to 4 years if unemployment and rental income/expenses are factored in). Overall satisfied with the trade off, 6 months of expenses for $1,700. For anyone else who can make the math work, I'd say go for it! The time to do it is when you're gainfully employed though, not once you've lost your job.
I can't stress enough, our plan is NOT to carry mortgage debt into our 70s, but to still pay it off in 10 years. The entire purpose is to provide additional security in a worst case scenario.