Crystals and nobs are an in app purchase. What you spend your nobility on is not. Crystals and nobs do not expire.
That section is related to purchased applications in order to avoid scams. That is all. Think about trial applications. All trials apps content and services expire after a limited time. Are trials rejected? No.
Hmm, if the boxes don't expire, they should be restricted to being open by nobs. Some of us spent thick coin to open ours before the expiry date. Perhaps we can open them with Psion?
They will make the box available to open by the key that can open for ten nobs. Expect the key to open plunder chests to be there for 10 and 20 nobs as well. This will help them make more gold by ppl opening chests with nobs then paying for keys as well.