G - for you I would recommend getting the Edge Pro Essentials Set: http://www.chefknivestogo.com/edproesset.html
. The Shapton Glass stones are awesome on the Edge Pro!
You might want to add the following items:
The Angle Cube: http://www.chefknivestogo.com/anglecube.html
. This is great for accurate measurements and logging/repeatability of your sharpening angles.
The DMT 2x6 diamond plate: http://www.chefknivestogo.com/dmt2x6diplfo.html
. It's got a different grit on each side and is the perfect size for flattening EP stones (which you'll need to do).
If you have knives that are dull and need a fair amount of metal removal to cut a new bevel, then think about a lower grit stone. The Shapton Glass 220 for the EP: http://www.chefknivestogo.com/shglst220grf.html
would be a good one. It'll save a lot of wear and tear on your 500 stone.
The above would be a killer setup IMO.
Regarding stone life, it depends on how much grinding you need to do on each knife, what kinds of steel, how much pressure you use, etc. Lots of variables there. Lower grits stones wear more quickly than higher grit stones. It's just the nature of the more coarse substrate on those stones. Your 4K stone should last a LONG time, since you'll just be refining and polishing a sharp existing bevel.
If you're trying to match the existing bevels closely (a good way to start out on the EP), then that creates less wear & tear on the stones than trying to cut new bevels at different angles, thinning blades behind the edge, etc. Use a sharpie to paint the edge and set your EP angle to a good compromise that matches the bevel on the majority of a particular blade. You'll find that a guided system like the EP will show where an existing bevel does not have a consistent angle throughout the blade. The Angle Cube will let you find out what angle is best for each knife so you can log that info and repeat it. You'll definitely need to keep a log with that many knives
Do some searches through this forum for great tips on using the EP. It's a much easier learning curve than free hand sharpening. You should be able to get really sharp edges after just a bit of practice.