Whether this has any bearing on it I'm not sure, but this seems to be affecting users that use wpa_supplicant more, though Windows users have also reported the problem.
The sessions *also* have a timeout. Read eap.conf.
Do you mean under the cache directive? If so that is set to 48 hours, yet failure occurred within 30 minutes. Our wireless controllers have a 1800 second client session timeout, forcing a reauth every 30 mins. Below is an excerpt of the radpostauth table for an affected user, it shows the user re-authing every 30 mins though the night. I migrated back to 2.1.8 (from 2.1.7) at 08:41 this morning. The client reauthed successfully once after the reload at 08:48, but then fails at the first 30min session timeout after that. 3843824 554694@swansea.ac.uk Access-Accept 2010-01-13 02:17:26 3845505 554694@swansea.ac.uk Access-Accept 2010-01-13 02:47:26 3846902 554694@swansea.ac.uk Access-Accept 2010-01-13 03:17:26 3848181 554694@swansea.ac.uk Access-Accept 2010-01-13 03:47:26 3849298 554694@swansea.ac.uk Access-Accept 2010-01-13 04:17:26 3850365 554694@swansea.ac.uk Access-Accept 2010-01-13 04:47:26 3851351 554694@swansea.ac.uk Access-Accept 2010-01-13 05:17:51 3852249 554694@swansea.ac.uk Access-Accept 2010-01-13 05:47:51 3853197 554694@swansea.ac.uk Access-Accept 2010-01-13 06:17:51 3854151 554694@swansea.ac.uk Access-Accept 2010-01-13 06:47:51 3855154 554694@swansea.ac.uk Access-Accept 2010-01-13 07:17:51 3856266 554694@swansea.ac.uk Access-Accept 2010-01-13 07:47:51 3857449 554694@swansea.ac.uk Access-Accept 2010-01-13 08:18:16 3858680 554694@swansea.ac.uk Access-Accept 2010-01-13 08:48:16 3860025 554694@swansea.ac.uk Access-Reject 2010-01-13 09:18:16 3860091 554694@swansea.ac.uk Access-Reject 2010-01-13 09:19:37 3860144 554694@swansea.ac.uk Access-Reject 2010-01-13 09:20:58 3860165 554694@swansea.ac.uk Access-Reject 2010-01-13 09:21:23 Thanks, Jezz.