With some protection products you can choose to make payments that are either guaranteed or reviewable.

Guaranteed: your premiums are fixed for the duration of the policy and will not increase.
Reviewable: your premiums are subject to change and will be reviewed at set intervals.

With guaranteed premiums you are fully aware of your outgoings for the duration of the policy. Reviewable premiums are distinctly cheaper at the outset, so this is well worth considering if you are on a tight budget.