Let me know if this is too pedantic, because I might just not be familiar with this particular usage, but calling this behavior "non-deterministic" seems like an abuse of the term.
From what I understand, it can't be predicted by the user -- it depends on factors such as application's memory image size, system load, idle time, etc.
As a user, I don't know when the app will go away.
Yes, the article seemed pretty clear that 1. disappearing an application is at Lion's discretion, and 2. that the behavior changes over time.
Perhaps if you really think about it, it's deterministic, but it's 'casually non-deterministic'.
So yes, I'll admit to abusing the term in its pure sense.
Don't add some non-deterministic 'feature' that messes up my model of where my apps are. If you must quit an app to recover resources, do it whilst pretending that the app is still running, because that's my model.
Perhaps, in regularly cmd-tabbing to running but documentless applications, I am some kind of uber edge (head) case, but I suspect not.