Since the actual documents of such contrasts became useless after their expiration, most of them were destroyed and consequently the surviving examples are very few, but it seems 10- or 20-year contracts were the most common, with a few examples of 30- or even 50-year contracts.
契約が満了すれば、契約書なども不要となって廃棄されるため遺存している物が少ないが、契約期間は10年もしくは20年が多く、30年・50年の例もある。