No chance on paying double payments! And doing some very rough maths, if we spent every penny we earn in the next 5 years - after taxes and pensions - we wouldn't be able to repay in that time. Unless we get some seriously tasty pay rises in the next years - and to give you an idea how likely that is, my salary has fallen 10% behind inflation over the last five years. And even then, we'd have starved to death, or frozen because our utilities had all been cut off for non-payment, or be in prison for non-payment of council tax. So yeah, we're not going to be able to manage to do it as quickly as you did!
The banks do work out how quickly you can pay off the mortgage if you eat nothing but porridge and baked beans and I think ours was 10 or 15 years.
However we did manage to find an offset (originally the only ones we could find, we didn't qualify for) so we're throwing all our remaining savings into that and it's going to make a significant difference. And once we have our head around just how finances are working out (a lot of bills will be going up as it's a bigger house, and we have to switch to fibre optic broadband) then we'll start overpaying within reason.
My captcha is JESTZ. Hee.