In some examples, this disclosure describes a method of operating a circuit. The method may comprise performing a circuit function under normal operating conditions, wherein performing the circuit function under the normal operating conditions includes performing at least a portion of the circuit functions via a characteristic circuit, performing at least the portion of the circuit function under enhanced stress conditions via a characteristic circuit replica, and predicting a potential future problem with the circuit function under the normal conditions based on an evaluation of operation of the characteristic circuit relative to operation of the characteristic circuit replica.