An Income Boost is intended to be a temporary support - think of it as a stepping stone to going it alone.
When you come to remortgage at the end of your term, you'll have the chance to remove the booster from your mortgage. So if your circumstances have changed, perhaps because:
your salary has increased, or;
you would like to add someone new to the mortgage.
If you meet the affordability requirements, then you'll be able to remove your booster from the mortgage.
For more details on the implications of an Income Boost for a Booster, check out our detailed guide.