Lifetime cover is pet insurance where the vet fee limit resets each year, so ongoing conditions can stay covered while you renew.
The key feature that sets lifetime cover apart from other policy types is the annual reset. Each year when you renew, the vet fee limit starts fresh, meaning a condition that developed in year one can still be covered in year three, five or beyond, as long as you keep renewing.
This matters a great deal if your pet develops a chronic or long-term condition. Something like epilepsy, diabetes, a recurring skin condition or a joint problem can require ongoing medication and treatment for years. With a time-limited or maximum benefit policy, cover for that condition eventually runs out. With lifetime cover it doesn't, subject to you renewing and the insurer's terms.
Lifetime policies cost more than other types. Premiums are higher to begin with and tend to rise more noticeably with age, because the insurer is committing to covering ongoing conditions year after year. For a pet that stays healthy throughout its life, a cheaper policy might in hindsight have been sufficient. But for a pet that develops something ongoing, the difference in what a lifetime policy covers versus a time-limited one can be substantial.
Getting lifetime cover in place early, before any conditions appear on your pet's medical records, gives you the best chance of those conditions being covered if they do arise.