What are the rules governing the duration and interruption of an unrestricted archery practice session?

Primary text

If they agree to shoot a set amount each day, it is permissible, as this accounts for potential fatigue or weakening in one or both participants despite their skill. If the contract is left unrestricted, it is permissible, and it is presumed to require immediate commencement and completion, like other contracts. They shoot from the beginning of the day until the end, unless an excuse arises, such as illness, wind, confusion among the arrows, or necessity for food, drink, prayer, or personal needs. These interruptions are implicitly excepted by custom. Rain also necessitates cessation as it loosens the bowstring and ruins the volley. If night falls, they cease, as the custom is to refrain from shooting at night, and the contract is presumed to adhere to this unless they specifically stipulate night shooting, in which case one can hold the other to it.