I agree for maintaining strength a 1x a week workout would probably do well (if increasing is not your goal). Also over use of high intense intervals too often may cause lack of recovery depending on your calories intake. So assuming just for lifelong health you would want to minimize calories without muscle and performance loss. The best way is just trial and error...plus some weeks you may get all your workouts in...some weeks you may not.
Mobility...try Yoga. It's a great active recovery and mobility workout. Plus a great stress reducer....that is if you are not wearing an Ipod with "Welcome to the Jungle" blasting...