Generally, franchisors do not grant perpetual renewals although some do. The reason that most franchisors do not do this is that it can be quite difficult for a franchisor to terminate a franchise agreement or to have sufficient grounds to refuse an automatic renewal under a renewal clause in a franchise agreement even if a franchisee is performing badly. Renewal clauses contain conditions which have to be satisfied if a franchisee is to receive a renewal but those conditions are sometimes subjective and, as a result, there may be uncertainty as to whether the franchisor is entitled to terminate and where there is uncertainty issues can end up in court. In view of the above, franchisors prefer a situation where after a fixed number of renewals, there is no contractual right in favour of a franchisee to renew. That has the advantage of being clear cut and, of course, a franchisor could always, in fact, renew the franchise agreement even though it is not obliged to do so. Indeed, a refusal to renew if a franchisee who was performing well wanted to renew, would make no commercial sense for a franchisor.
Generally, in a five year term you would expect two automatic renewals, in a ten year term one automatic renewal and, in the case of the much rarer twenty five year terms you would not expect any renewal.