Contrary to popular wisdom there is nothing fundamentally wrong with debt. The problem is with expensive debt. It’s the interest rate attached to most debt that makes the debt a bad thing.
If you could borrow £100 and pay back £100 a week, or even a year later, there’s not really anything wrong with that.
So the first instance in which it may not be important to pay off a debt as quickly as possible is when the debt is essentially free.
The second scenario is a little more complex.
If you can borrow money with an interest rate of 3% but you’re buying an asset that will reasonably appreciate at 10% over the same period, you’re still going to benefit to the tune of 7% over the lifetime of the debt.