Force reauth possible? (INTERNAL)

Hi I may have asked this before but can't find any references or replies. Anyway, I'm running FreeRADIUS 3.2.6 and I'm using EAP-TLS only. When a device has authenticated it seems to be in that state forever until it reboots or loses its network connection. Is there any parameter I could set that would force my devices to re-authenticate after a certain amount of time? ./PerW Sensitivity: Internal