Took the words right out of my mouth lupin.

You don't need a medicine chest or anything. Frequent water changes is the only way to keep you fish in good health. Clean water = healthy fish = better immune systems = less chance of contracting diseases. On top of that, the only chemical that you should be adding to your water on a regular basis is dechlorinator. Everything else should be temporary if even used at all. The osmotic pressure from the total dissolved solids (TDS) of adding chemicals and other things in your tank is not good for the fish. It will most likely do more harm than good. So keep chemicals and medication usage at a minimal. I don't think I've had any disease outbreaks in over 6 years, no chemicals, just weekly water changes.
Also I wouldnt worry too much about snails. I'm too lazy to keep live plants, as most of my fish tear them up and uproot them so I've never kept any and never once did I find a single snail in any of my tanks.
Btw, I don't think just because someone has been keeping fish for a long time means they know what they're doing. I have friends who are relatively new to the hobby (less than 2 years) who practice better fishkeeping habbits than some other people I know who have been keeping fish for 20+ years.