If these are mainly for investment rather than frequent taking out and loving, then acid-free paper envelopes would be ideal (they are sold specially for coins). The first, last and most important thing ever at all times with no exceptions is - KEEP THEM DRY!!! Temperature doesn't matter too much for silver, copper and bronze (and gold), but a dry humidity-free atmosphere is paramount. The second thing is to keep them free from pollutants - PVC, coastal salt in the air, acids, fumes, dyes, fingers etc. Lustre may fade somewhat over the years but it won't disappear if the coins are stored with care. I use the Lighthouse self-adhesive 2x2 coin holders, are these then less than ideal for top condition coins? If so I had no idea and am a bit shocked (although I am a naive and ignorant relative newbie!) Paul