I agree with Pavel here from my own experience. Doing S&S 3 times a week is enough to stay very fit and strong, and keeping the cardio-vascular system strong also. S&S involves 100 heavy swings each session followed by 10 getups.
Now, this is hardly the only way to stay fit!
A more natural way is to go on long walks about every second day; in my experience 75 minutes a walk is the right amount. Mixing in any amount of running into this walk makes the walk just so much better.
In fact, my personal daily exercise hierarchy goes like this:
1. Judo training - blows the others out of the water.
2. Long walk with runs mixed in if possible for 75 minutes - frankly speaking better overall exercise than anything with weights - more natural for body shaping and better for cardio-vascular and structural aspects.
3. S&S - only takes 30 minutes and can be done in my house - more strength-intensive than the above but also more demanding than walking. Kind of a "perfect" exercise, and extremely efficient given the limited time it takes.
4. GTG strength lifts - no sweat so unnecessary to shower right after; deadlifts, military kettlebell presses, ring dips, chinups, kettlebell goblet curls...
If I can do 1 I do, if not then 2 if not then 3 etc...