I use Akonadi and Kmail ; several times per day, I have to use "akonadictl stop" and start it again because it stops retrieving my new emails. I have to do that 3-4 - sometimes 5 times a day. It's really annoying, because I cannot tell when it stops checking for new emails ; if I don't get new emails for like 1 hour, I assume it stopped checking and I restart Akonadi. I use Arch Linux with up-to-date packages.
This bug stopped happening for a while now.