Moe,

On your 15 years left at 7.5%, you'll pay $66,900 in interest.

Assuming you get a rrate of 4.25%, you'll pay $35,400 over the next 15 years, and your payment will drop from $975 P&I to $752.

Keeping your P&I payments at $975, you'll pay that note off in 10 years or so, saving an additional $11,100 in interest.

Depending on which route you choose, you could save $31,500, or $42,600.

I suggest the latter model.

As far as me choosing a 15 year note, I have a contract with a buy-out feature every year I work there. Odd for a banker, but it gets more expensive for them to release me every year.