There's no need to update valid technologies unless the cost of maintaining them outweighs the upgrade cost. Take into account some legacy systems can increase your vulnerability if not designed for the current threat landscape.
A breach isn't quite as big a deal as we've been told. That is if the findings of a new report are to be believed. Authored by Sasha Romanosky, a policy researcher at the RAND Corporation, the report undercuts one of the great cliches of the cyber-security industry: that breaches are expensive.