Welcome Marcos,
I think you are now the "eldest" elder-statesman on APK. At 55, I think I USED to be. (This particular forum topic was a result of me ordering the videos a year ago and M2 discovering how old I was.) Your perspective will be much valued, not only from your age, but from your background. Good to have you on board.
Wow Dave!
I just answered your e-mail and came back to the site. 55! Sorry to steal your thunder. Blame my mom.
When I talk to students who are in their mid-twenties or even younger and try to teach them something and they launch into a long discourse about how, "I can't do that because . . .", I feel frustrated.
I'll admit, I'm sort of out of shape right now. But, that's my fault. I have hurt myself many times. Still, I feel too ashamed to use that as an excuse to stay on the couch.
So what if I can't do a back flip off a roof? And I'm not convinced that it is impossibility. The practice of PK is still the coolest, most practical use of our ultimate resource (the body) that I can imagine. It can be used in real life.
As I mentioned, I train police. We have many independent groups of police here. But, what bothers me is that they receive no additional training after the Academy. We've got guys that are F-A-T. We have young guys that can't even touch their toes, and these are the "fit" ones in their 20's.
The average guy (or gal) wants to get a desk job and vegetate for the rest of his or her life. Me, I'm no Schwartzenegger or Dave Draper but, I can still bend over to tie my shoes.
All of they guys that love Parkour and want to practice it should do it (safely) and expect support from people who have influence in their lives. Everything will work better

I'd like to come as close as possible to doing what the kids are doing on video. No one to tell me no. Baby-steps and caution. As I do this, I want to set the pace for some of the younger people here in my city. I would like to introduce Parkour here as a respectable art. (Emphasis on art.)
The kids fascinate me. But, as in my art of Aikido, I think that it is something should be a life-long pursuit and not just something to do until you incapacitate yourself permanently.
Just so those who are not in this age group don't get me wrong, you young guys absolutely inspire me. I just want to encourage you to take necessary precautions and the time necessary to master your art. Mastery is a level above just being able to do something. It implies something near total control.
My art is physical as well as mental/spiritual. I'm still practicing and teaching after almost 30 years. I've seen others burn out after a short run and never take up another physical activity. Just imagine the possibilities if you can keep on improving your art for 30 - 50 - 60 years!
I'm a (practicing) fan.
Marcos