Smoked malt definitely does lose potency over time. I just did a rauchbier split between 05 and 34/70 with some Briess CW malt that has to be at least 4 years old, ~11% of the bill. I had one of the ales last night and the smoke flavor is VERY subtle, not nearly as strong as the last time I used the malt a few years ago. Just bottled the 34/70 the other day so I haven't tried it yet.