Hello,
I'm getting back in shape after a few too many years of neglect. I've always wanted to train in kung-fu and have located a Northern Mantis style school that I like. My question is: Is it good for longevity and health? Is Northern Mantis something I can do to a ripe old age? Thanks.

Theoretically, yes. I've seen some pretty old masters of the style perform it, and they looked as healthy and flexible as ever. But your best option is still to give it a try and see for yourself.

Any traditional Chinese style is meant to fully respect your health and general physical integrity. Even though some might look like they push your body to its extremes (and they do), they never twist any joint in a un-natural angle, and therefore should be perfectly safe in the long run.
The problem is, you need a truly competent instructor who'll pay attention to this and won't let you damage yourself by doing it wrong (for instance, a good master should always notice and correct you if you extend your knees too far forward when in a "horse" or "bow" stance: it's not only bad form, it's bad for the knee joint)...
So in the end, it mostly comes down to the quality of the school.

Thanks Shi. That makes a lot of sense.

I have a special interest in longevity programs. Over the years of coming into contact with martial artists and teachers from a wide range of disciplines, I have developed the opinion that pretty much any regular martial arts training is going to result in at least a more youthful old age, if not a longer life. This would be a great study to do!

I currently am taking 7 Star Mantis and my teacher learned from another master who is currently in his 60's i believe and my teacher being 33 still gets thrown around by his master. The thing is as long as your doing it right, it can def be something you can study for a very very long time and still be affective. Personally i love it, even though i have only been training for about 2 years. i would recommend it.

I would say that any martial art, per quality instruction would deliver health-longevity benefits.