If you have no possibility to send via RADIUS Session-Timeout attribute or you are using chap-secrets and want to reestablish sessions every N time

[common]
session-timeout=n

[pptp]
session-timeout=n

[l2tp]
session-timeout=n

[pppoe]
session-timeout=n

[sstp]
session-timeout=n

[ipoe] already has it.

session-timeout in [common] section has less priority than session-timeout param define in some connection type section. But this param can be overwritten via RADIUS attribute Session-Timeout