[MlMt] Disable app nap not working?

[Seebs]

So, I got this useful tip from the list of disabling app nap for 
MailMate, and life has been good...

Until this weekend, when Mailmate was pretty quiet and then I clicked on 
it and I had 120 messages some three days old.

Whoops.

Is there something else I might need to do? I have double-checked, Get 
Info continues to show the app as having "Prevent App Nap" selected. And 
it is pretty important to me that Mailmate actually check for mail 
actively.

No, I can't "remember to bring it to the foreground". My brain does not 
admit the creation of a habit of doing a thing that doesn't have any 
effect except every three or four weeks suddenly it matters.

-s