> Your kids might be dead by the time it's paid off, you'll never own it.
Exactly right. I don't know anyone who buys with the intention to own.
Effectively you rent it from the bank. I don't mind, I mean I don't mind renting from the bank. I pay off my mortgage (2% per year, so 50 years) but only as long as its reasonably high, in order to lower interest rate costs and reduce the risk of being under water.
I have no interest in paying it off completely, so I'll stop paying 2% per year when the mortgage is down to e.g. 40% of the value. Obviosly as a banks have zero interest in your customers loans shrinking, it's lost revenue!
The big downside of very long mortgages is that it brings up nominal prices, and thus the volatility