While this may certainly be a driver bug, all my disconnection issues vanished after upgrading to a new WiFi router.
Old router with iwlwifi disconnect issues: BUFFALO|WHR-HP-G54 125M R
New Router without any problems: TP-LINK| ARCHER C7 R
Not ideal, but apparently a feasible "workaround" (if you need a new router anyways).
While this may certainly be a driver bug, all my disconnection issues vanished after upgrading to a new WiFi router.
Old router with iwlwifi disconnect issues:
BUFFALO|WHR-HP-G54 125M R
New Router without any problems:
TP-LINK| ARCHER C7 R
Not ideal, but apparently a feasible "workaround" (if you need a new router anyways).