In general, new particle lifetimes are so small than the decay looks instantaneous from the detector standpoint. Any particle whose decay would be recorded as a displaced decay (compared to the primary collision point) can thus considered as long-lived.

Typically, from the LHC standards, we consider particles flying over distances ranging from millimeters to a couple of dozens of meters. Of course, long-lived particles could even be more long-lived ("stable" is the maximum).