Do not be naive: nobody lives to 150 years. The Banks will figure if you are 80 (me too, btw, so no offense here), you will not pay the mortgage of 25 years, even if you have a good credit refference. They will refuse you on other issues, but will never say, "sorry, you are too old".
The ONLY way they would give you one (should you be the 80 year old person), is AGAINST another real state, either paid in full (its value is higher now, because it was paid though long tears, but the real estate value has grown, so the Capital they will receive if they have to sell it, will double or triple from the original mortgage). That way, they will always have something to chew on.
The other chance is if the house or property against which the Mortgage is given is partially paid and its reassert value is more than 40%. Try CHIP (Canadian Housing Income Plan). You don't have to sell or pay AS LONG AS YOU live there.
btw, the word Mortgage means Deal With Death. How truth. Sorry if I seemed synical, but I am of the "good image" banks are trying to portray. They are the greatest of all robbers.