These weren't directed at me, but
Is it necessary for you to "build cardio" while running?
Yes, the events I train for (Marathon, Triathlon, Various Mudders) require me to run for training. This is a much to build muscle strength as it is to build cardio- cycling and swimming are good too, but anyone who has gone from swimming to biking to running knows these activities have different ranges of motion.
Are you a professional runner? Do you need to run such and such distance? What is rushing you so much?
I am not a professional, but I am a pretty serious hobbyist. A very large part of my physical improvement over these past several years has been to push myself in training toward an event I want to complete. Right now, I'm prepping for my first 1/2 marathon, with a full marathon distance on plan within the year. The 5k "limit" for pavement running in the VFFs is preventative to this goal. Also, I am getting older (37) and even though I strength train carefully, and watch my vitamin intake religiously- I still worry about injury. I've been a VFF runner for 2 years, and my form has changed radically in that time, but still if I run more than 5k on pavement in VFFs my feet hurt. Running on soft ground in the VFFs I've covered triple that distance- this causes me to believe that my form+VFFs+pavement= injury risk. I continue to work on my form, but I want to race a couple pavement races this year so I've switched to the Kinvaras (I've got 3 pairs now) and found they suit my form very well, while providing a little cushion that keeps my feet comfortable.
In the meantime, I am using my Komodos for crossfit, and loving them during the soft ground sprints (I run in the grass)
The older you're the longer it is going to take to rebuild your body. The more patient you need to be
Drinking milk, and eating some "white" cheese might help a little
LoL- I'm a vegetarian- BUT I do get those doses of Vitamin D and Calcium from alternative sources. Also, the older I am the longer it takes to heal, so giving my body a little extra shock relief seems like long term maintenance for my joints.
I realize there are lots of people here in particular who may feel I'm taking a shortcut, but if I was really interested in taking any sort of "easy way" then I'd still be on the couch playing COD instead of out doing work, and covering miles in whatever shoe I've chosen.
I'm a big believer in using the right tool for the job, and when it comes to pavement running, I think the right tool is the Kinvara. It is a choice, much like the choice i made to try those "weird toe shoes". When running on softer stuff, the VFFs are still at the top of the roster.