I had to give up mountain biking when I started breaking things on my body. I have to say though that your post made me really miss it. I used to ride with a bunch of guys every Saturday morning of the year - no excuses were granted for weather conditions. Below freezing temperatures are actually some of the best riding because the trails aren't muddy. Most of the time on the technical downhills the best thing to do is to just let go of the brakes and go. And those hyper expensive suspension forks - they're worth it. If you can get the dampening right they'll keep your front wheel in contact with the ground, you'll have much better control, and consequently be able to ride much faster on the bumpy downhills. Best of all, you'll be able to keep up with riders who are better than you.