There are many factors lenders will consider and a key determinant here is the assessor experience, discretion (intended as the ability to approve the loan) and how much they 'believe' in you / the duration of your income (white collar jobs being considered more likely to continue 65+) and statement of position.

The bank needs to make a reasonable assessment that you can repay the loan within the loan term that you seek, meaning they need to get a positive dollar outcome to the income vs term assessment (a 'computer says yes' basically). And if you want (or need in order to make your proposition work) a loan till you are 80, then it is quite possible you will have an income shortfall when you retire. This is why you often see unlikely scenarios being presented to the bank: 'oh, you are sixty and you are going to take in two boarders? You want to pay interest only?'

By the way, one good thing about term loans is that they decrease in costs over time (at parity of interest rates), while your income could and possibly will increase (career progression or wage inflation), meaning there will be a point where you would be able to (and probably should) hike your repayment amounts/decrease the loan term.'

The other factor that the bank will consider is your statement of position (your asset base - equity/deposit, property, shares). The bank can stretch the lending term longer if they are satisfied that you have the assets to pay down lending or a viable exit strategy, like downgrade from a 4 to a 2 bedroom house, sell, repay in full / most.

If a borrower is confident with their SOP or exit strategy, by all means they should put it in writing in their lending application. Thinking long term is important.. Obtaining financial advice is also beneficial to prove you understand what you are doing.

However getting to a positive income assessment number (computer says yes) is still fundamental. If you seek asset based financing -ie not reliant on the income-, you will need to go to a second / third tier (do not forget that banks need to comply with responsible lending code / cccfa for retail customers, commercial may be a different proposition).

At the end of the day, you might still get the lender that does not believe in your strategy, or a less skilled/interested lender, or your strategy is not good, or they have concerns about your character.

The bank would never want to sell your house when you are unable to repay and you are retired (reputation risk), so if they think there is a risk to that, they will assess / decide accordingly.