The coin age shouldn't be lost if there isn't a confirmed transaction for the coin stake age. However, if you really want to be sure one can always use the repair commands..And in the most extreme case one can rebuild a wallet using only the keys and force the client to rely on only the blockchain itself which is all that it could "see" at that point..It isn't that hard or even that many steps but it does take some patience and care.
Thanks for your information. After type the command "repairwallet" in debug window, the lost balances came back to my wallet. What a simple step that I even not trying to find out!
I had this wrong cognition just because the "cryptorush" trading site claimed that they lost plenty blackcoin in staking stage when they updated the wallet version. Maybe the real reason of their blackcoin balances mismatch wasn't due to wallet update.