Since the interest is rolled up and added to the loan sum, you don't have to make monthly payments. This is repaid when you pass away or enter long-term care.
On the other hand, if you have the ability to make payments to service the interest or even some of the capital then you can do this. If in the future, you no longer can afford to make payments to the lifetime mortgage you do not have to make any. Just call your lender and advise them and they will start to add the interest to the balance of the mortgage, so no payments are required.