There are a lot of experts out there who want to tell you how to extend your life, improve its quality, and empty your wallets.
I say that happiness is the key to a good life, and happiness comes from balance. If it makes you happy to weight train, cycle, swim or run, do it (if it does not make you happy then why the hell do it?). If you do exercise to excess it may be as counterproductive as not doing it at all - there is a reason why top sportsmen (and women) all have personal physios. IMHO though, its those who do no exercise that do most harm to themselves, especially when linked to a sedentary working life.
Been a swimmer, a long distance runner, and a gym monkey. Enjoyed it all. Now I work a physically demanding job, and walk the dogs. Too much running made my knees unable to cope with protracted heavy exercise, so the muscles are going south, and shrinking. But I am happy, I have a strong heart and excellent blood pressure.
I note you guys are also on very high protein diets - that's good if you are in control of it, but it can be as harmful as drinking too much alcohol, unless it is a professionally controlled diet.
This is not to put anyone off of any form of exercise either as a hobby or a passion. Just keep a balance as with all things in life.