On long lived diffs and tickets I always find myself clicking "Show older changes", Personally I don't think we are showing enough history by default and I think that maybe we should show more?
I can't think of a concrete number that will satisfy this case of "on long lived diffs". Either you want the full history or you don't. Not sure 5 more stories will be enough (and creates significant clutter for everyone else).
I think this is the kind of interaction that many people with have an opinion about, and they will vary wildly. What's better for some, is decidedly worse for others. Arbitrarily changing it doesn't really solve the problem enough, and the entire interaction probably needs rethought.
(We could theoretically fiddle with this and include some time constraints and stuff but I suspect this rule is already the best rule we're really going to get, given how contentious/subjective the subject is and how little complaining we hear about it, relatively.)