You have to be very careful with silver if your goal is that it never becomes discolored. Unlike gold coins, silver is effected by moisture and other elements so that it can tone/discolor over time even if you are careful. I don't know any specific ways to recommend without purchasing items specifically made for the goal you mention. If you are keeping your coins in a safe or coin box, etc., you should keep a desiccant/silica gel in the safe or box (not in the coin tube itself) to capture moisture. If you are keeping the coins simply for the silver value, I would not be too concerned with any toning or discoloration.
Make sure whatever holder you use is PVC free and is made specifically for holding coins. Never keep your silver coins in the plastic PVC flips you get from the coin store when you buy a coin.
If the coins are valuable to you outside of the fact they are silver, I like the airtight brand individual holders. They aren't cheap if you have a lot of coins you want to protect, but I have found they work well. Tubes in general can sometimes let in moisture. I have seen American Silver Eagles from the 90s starting to look pretty discolored and they were left in their tubes since day one. I have a couple of tubes of 1982 Mexican Libertads that were never opened from day one (that is, until I bought them recently). When I opened them I could see the top 2 coins were almost black in places due to moisture seeping in through the top of the tube. The rest of the coins looked great, except some showed darkening on the rims. None were completely what you would call perfect looking.
There have been some very old Morgan silver dollars released that have been in vaults that were in stored bags since they were made and they look perfect, so maybe the environment itself is more important than the specific holder, with respect to keeping out moisture, humidity, etc.
If the coins are really valuable, perhaps consider having them graded by NGC or PCGS, and they put them in pretty good slabs when they grade them.
Jim
