What is it the wears out on a cartridge?

Modern suspensions use space-age polymers that won't exhibit deterioration for a few decades. In addition to that, their properties remain consistent over a large range of temp and humidity.

Line-contact or micro-ridge styli will last longer than conical or elliptical styli; because the former develop less friction (even though most cartridges that use them require higher VTF)

Keep your records clean. You don't HAVE to be a fanatic, but if you're NOT, then you'll wear out your ears faster than your stylus!

Don't use liquid stylus cleaners. First, they don't work. And second, if your cartridge has a tubular cantilever, the liquid could capillary up the tube and dissolve the suspension. Do use the Onzo Zero-Dust before every side (more for your ears than your stylus.) Every half dozen records or so, clean the stylus with a Mr. Clean Magic Eraser device you have to make yourself (it's easy) For more info on the ME, do a forum search. But the ME is the ONLY thing that will clean your stylus sparkling new -- including the crud that builds up between the back of the diamond and the bottom of the cantilever. Follow with the Onzo to remove any loose debris.
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Line-contact or micro-ridge styli will last longer than conical or elliptical styli; because the former develop less friction (even though most cartridges that use them require higher VTF)

In theory, yes. In practice, only if the alignment is correct to reduce the stress (contact force/unit area) on the groove walls.

All very true. And for the easiest way to set the stylus rake angle (SRA) and other delights, read this thread:
http://forum.audiogon.com/cgi-bin/fr.pl?eanlg&1140840022&openmine&Nsgarch&4&5&st0

BTW: VTA (both as an idea and as a number) is a useless concept and impossible to achieve, because:
1. No cartridge in existance has physical properties that would exactly match a given cutter head (which it would have to do to even THINK about setting VTA).
2. Cutter heads are different from each other anyway, and
3. Even if a cartridge matched (at least) one cutter head, and COULD be so adjusted, you'd still have to set the SRA to get the stylus to lock into the groove properly; and doing so would throw off your VTA adjustment anyhow!

So anyone who discusses VTA as being an important parameter (people like Mikey Framer) is a charlatan who knows nothing about physics or mechanics! So there ;-)
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