In England, currently and for most of the last fifty years, the standard length of the mortgage term is 25 years.
A mortgage can be either a capital-and-interest mortgage, or interest-only. In the former, you pay off part of the original loan each month, plus the interest on the amount borrowed. In the latter, you only pay interest each month, and the original amount borrowed never reduces: you pay premiums on a life insurance policy, additionally, which is designed to pay off the original sum borrowed at the end of the 25 years.
No one in England thinks that a 25 year loan has any drawbacks. The main point to appreciate is that the longer the period of the loan, the less you need to pay each month, because you are repaying the original loan - the capital - over a longer period of time. Thus, in principle, a mortgage is easier to repay the longer the term is, because the monthly payment is less.
If you have a 12 year mortgage, you must pay back the original amount borrowed in half the time: the capital element in your payment each month is double what it would be if repaid over 25 years - i.e. if repaid over a period twice as long.
Only if the borrower is less than 25 years away from retirement is a 25 years mortgage seen as a bad idea, by the lender - because, obviously, the lender relies on the borrower having an income sufficient to keep up the repayments.
There are many complicating factors: an interest-only mortgage, where you pay back the original amount borrowed from the maturity proceeds from a life policy, puts you in a situation where the original capital sum never reduces, so you always pay the same each month. But on a straight repayment mortgage, the traditional type, you pay less and less each month as time goes by, for you are reducing the capital outstanding each month, and because that is reducing so is the amount of interest you pay each month (as this is calculated on the outstanding capital amount).
There are snags to avoid, if you can. For example, some mortgage contracts impose penalties if the borrower repays more than the due monthly amount, hence in effect the borrower faces a - possibly heavy - financial penalty for early repayment of the loan. But not all mortgages include such a condition.
If house prices are on a rising trend, the market value of the property will soon be worth considerably more than the amount owed on the mortgage, especially where the mortgage debt is reducing every month, as each repayment is made; so the bank or other lender will not be worried about lending over a 25 year term, because if it forecloses there should normally be no difficulty in recovering the outstanding amount from the sale proceeds.
If the borrower falls behind on the repayments, or house prices fall, he may soon get into difficulties; but this could happen to anyone - it is not a particular problem of a 25 year term.
Where a default in repayment occurs, the bank will often suggest lengthening the mortgage term, from 25 years to 30 years, in order to reduce the amount of the monthly repayment, as a means of helping the borrower. So longer terms than 25 years are in fact a positive solution in a case of financial difficulty.
Of course, the longer the term the greater the amount that the borrower will pay in total. But the longer the term, the less he will pay each month - at least on a traditional capital-and-interest mortgage. So it is a question of balancing those two competing factors.
As long as you do not have a mortgage condition that penalises the borrower for paying off the loan more quickly, it can make sense to have as long a term as possible, to begin with, which can be shortened by increasing the monthly repayment as fast as circumstances allow.
In England, we used to have tax relief on mortgage payments, and so in times gone by it did make sense to let the mortgage run the full 25 years, in order to get maximum tax relief - the rules were very complex, but it tended to maximise your tax relief by paying over the longest possible period. But today, with no income tax relief given on mortgage payments, that is no longer a consideration in this country.
The practical position is, of course, that you can never tell how long it might take you to pay off a mortgage. It is a gamble as to whether your income will rise in future years, and whether your job will last until your mortgage is paid off. You might fall ill, you might be made redundant, you might be demoted. Mortgage interest rates might rise. It is never possible to say that you "can" pay off the loan in a short time.
If you hope to do so, the only matters that actually fall within your control are the conditions of the mortgage contract itself. Get a good lawyer. Tell him to watch out for early-redemption penalties. Get a good financial adviser. Tell him to work out what you will need to pay in additional premiums on your life policy if you are considering taking an interest-only mortgage. Try to fix your mortgage rate in the first few years, for as long as possible, so that in your most vulnerable period, with the greatest amount owing, you are insulated against unexpected interest rate fluctuations.
Only the initial conditions can be controlled, so it might be prudent to take as long a term as possible, even though a prudent borrower will leave himself room to reduce that term, and a prudent lender will leave room to extend it, in case of unpredictable changes in the financial circumstances.
In England, most lenders are, in my experience, reluctant to grant mortgages for less than 25 years. That is simply a policy. Rightly or wrongly, the borrower usually has no choice about the length of the mortgbage term. Hence, in the UK it can be difficult to find a choice of interest rates based on differing mortgage terms. I am aware that the situation in the USA is rather different, but if I personally were faced with the choice I would be uncomfortable about taking on a short term mortgage, because of the factors I have outlined above.