after 2.6 friendship ends.

[Mister Ed]

While there may not be a specific rule as to the exact length of time, at least it is clear that the "reasonable time" resets any time you are winning the combat, so if you are winning, and others do stuff to stop you from winning within a "reasonable time", then you do something else so that you are winning again, they get ANOTHER "reasonable time" to respond to that.