Not sure I understand if you’re asking for map round time or multi round/map session.
For round times, I’d prefer to play like in RtCW -where maps had default time ranging 8-15 minutes AND also a possibility for server admins to set whatever round time they want per map.
With “reasonably” short round times you can get some multi round/map carnage even if you only have an hour to spend before dinner.
However if the question is about session times rather than round times, then I’d say I play more than an hour per session.
For incitament to play longer sessions, I’d say clanmates around and well admined servers (for which the server tools to do that has been in general sadly reduced in newer games).