I was continually connected for a record 8 days. Very cool, thanks to everyone involved.

Just now, suddenly I lost connection, and then NM used 100% CPU of one core.. It never did this before, and so I am not sure if this is a different issue and whether I shall file a separate report. 

Looking at the log, I don't think so, though. The log from the last few days is attached. There is a curious part in there, right when it lost connection. I don't think it should disconnect from an existing connection because it found a better version of that very same connection, which it then fails to reestablish:

Oct 10 19:14:09 chronic NetworkManager: <info>  eth2: link timed out. 
Oct 10 19:14:09 chronic NetworkManager: <info>  SWITCH: found better connection 'eth2/kleinehoelle' than current connection 'eth2/kleinehoelle'.  same_ssid=1, have_link=0 
Oct 10 19:14:09 chronic NetworkManager: <info>  Will activate connection 'eth2/kleinehoelle'. 
Oct 10 19:14:09 chronic NetworkManager: <info>  Device eth2 activation scheduled... 
Oct 10 19:14:09 chronic NetworkManager: <info>  Deactivating device eth2. 
Oct 10 19:14:10 chronic dhclient: There is already a pid file /var/run/dhclient.eth2.pid with pid 7345
Oct 10 19:14:10 chronic dhclient: killed old client process, removed PID file
Oct 10 19:14:10 chronic dhclient: DHCPRELEASE on eth2 to 192.168.1.1 port 67
Oct 10 19:14:10 chronic avahi-daemon[6328]: Withdrawing address record for 192.168.1.101 on eth2.
Oct 10 19:14:10 chronic avahi-daemon[6328]: Leaving mDNS multicast group on interface eth2.IPv4 with address 192.168.1.101.
Oct 10 19:14:10 chronic avahi-daemon[6328]: Interface eth2.IPv4 no longer relevant for mDNS.
Oct 10 19:14:10 chronic NetworkManager: <info>  SUP: sending command 'DISABLE_NETWORK 0' 
Oct 10 19:14:22 chronic NetworkManager: <info>  SUP: response was 'TIMEOUT[CLI]' 

Then the log is busy with NM doing stuff, probably trying to reestablish, which ends with a severe error:

Oct 10 19:14:47 chronic NetworkManager: ******************* START **********************************
Oct 10 19:14:47 chronic NetworkManager: (no debugging symbols found)
Oct 10 19:14:47 chronic NetworkManager: Using host libthread_db library "/lib/tls/i686/cmov/libthread_db.so.1".
Oct 10 19:14:47 chronic NetworkManager: (no debugging symbols found)
Oct 10 19:14:48 chronic last message repeated 12 times
Oct 10 19:14:48 chronic NetworkManager: [Thread debugging using libthread_db enabled]
Oct 10 19:14:48 chronic NetworkManager: [New Thread -1212520784 (LWP 7332)]
Oct 10 19:14:48 chronic NetworkManager: [New Thread -1229309040 (LWP 7344)]
Oct 10 19:14:48 chronic NetworkManager: [New Thread -1220916336 (LWP 7337)]
Oct 10 19:14:48 chronic NetworkManager: [New Thread -1212523632 (LWP 7334)]
Oct 10 19:14:48 chronic NetworkManager: (no debugging symbols found)
Oct 10 19:14:48 chronic last message repeated 4 times
Oct 10 19:14:48 chronic NetworkManager: 0xffffe410 in __kernel_vsyscall ()
Oct 10 19:14:48 chronic NetworkManager: ******************* END **********************************

Apport did not come up, and I rebooted . After logging in again, NM did not reestablish and showed the WPA key dialog. Then I had to perform the usual procedure as already described above. The first timestamp in the log after rebboting is 19:17:15