Critical illness cover pays a tax-free lump sum if you’re diagnosed with a critical illness during the term of the policy. You decide on the length of the policy: many people choose to have cover until their kids have flown the nest, until the mortgage is paid, or until they plan to retire.
Think of critical illness cover like car insurance: you pay every month or year for it and hope you never ever need to use it, but you feel better knowing it’s there. Just in case.