I've been thinking about refi for a while since the interest rates are so low. Financially it only makes sense to me if I get an interest rate that's 1% below what I'm currently on (4%). Assuming a closing cost similar to that which I paid when I bought the house and keeping my monthly payment the same (I currently overpay):
If I get a 3.0% rate, I will save $7,500 over the life of the mortgage
If I get a 3.25% rate, I will save a whopping $2,185 over the life of the mortgage (10 years 3 months)
If I get a 3.5% rate, it will cost me $3,387 extra
Sitting now with the oil & gas market in the toilet and my job uncertain, I'm very happy with the position I'm in - if I can afford it, I'll put extra towards the principal but if I lose my job, my savings will allow me to continue paying the mortgage at the minimum rate for a year while I try and sort my life out. Optimizing is all well and good but it's sub-optimal to get stuck where you desperately need to sell your house because you've lost your job and can't make the payments at the same time when no one is buying!
It seems like refi is only worth considering if you can drop your rate by 1% without paying extra for points.