Traditionally, this was 25 years but it can be longer or shorter.
If you go for a repayment mortgage (also known as a capital and interest mortgage), the monthly payments will be higher, but by the end of the term you will have cleared the entire debt.
Several lenders now offer terms of 40 years or more.
A loan of this length may seem very attractive, as the monthly repayments will be quite a bit lower than for a standard term.
However, because you are repaying the money over longer than normal, you will end up paying far more interest.
And do you really want to be paying a mortgage when other people your age are debt-free and thinking about retiring?
The shorter the term you choose, the higher the monthly payments, but the upside is that you will be debt-free faster.
To help you decide on the length of your mortgage term, read What mortgage term should I choose?