In New Zealand, Australia and England, it is normal to see confidentiality agreements that continue to apply to information for so long as it remains confidential, that is generally indefinitely. However, the restrictive nature of these agreements means sometimes these agreements are unenforceable.
However, if confidentiality agreements are restricted to a certain timeframe, that might not amount to taking reasonable efforts to maintain the secrecy of the trade secrets, and trade secret protection could be lost even if the trade secret has not been made public.
One solution to this problem is to have a split confidentiality obligation, where the obligations relating to trade secrets apply indefinitely, but the obligations relating to all other confidential information apply only for a limited period. It is crucial though to demarcate the obligations through a legal agreement, including often a list of information.