I've been a Canon junkie since I inherited an the AE-1 back in 1990. Moved up to an EOS Rebel, where I bought a few telephoto lenses. The EOS lenses are interchangeable with the Canon DSLRs, so you're really buying into the lenses, since the technology in the actual camera bodies are ever-changing with new updates every six months or so.
Still, my 300D is going strong for years without a hitch, as long as you take basic care of them (no drops, no hits, always hold on tightly and/or carefully), clean out the sensor every so often. The DSLR Nikons use the same principle as the Canon; the lenses can be 20+ years old, and they still work with most of the latest equipment. Of course, the newest lenses always have a few more tricks like image stabilization and the like.
Basically, once you go DSLR, you find it hard to go back to point-and-shoot, although when you have a kid or two, it's nice to have a tiny camera ready on the fly instead of a bulky DSLR, when you have tons of other stuff to carry as a parent.
Also, don't run out and buy one of these cameras the day before a big event; they can take a few weeks to really sort out the finer points and neat little gadgets each beholds to do things right. Get a good illustrated book or two on how to use the camera (there's still things I discover how to perfect many years after initial ownership), and one on tips and tricks for composition, ideas, concepts, the "nuts and bolts" of a camera, and science of light and color. You'll also want photo-editing software and a good image browser that doesn't suck (like the ones that come with your operating system). And a spare battery!
It all sounds mind-boggling, but the important part is that you have fun with it, and not expect every shot to look perfect each time. You learn and learn and learn some more with each shot. Take notes, find others that are interested, and share ideas. Heck, some of my best and most interesting (in my opinion) shots were total experiments without regard to the suggestions the little microchip the camera suggests for settings...that's how you really move forward with it as a hobby.
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