That really relates to the probe, the meter, and the conditions the probe is in.
Only trial and error will let you know for your system. I've had them last for many months without drifting much, but then suddenly something can happen and drive it out of calibration (a power failure, stuff gets on the probe tip, etc.).
I'd typically recommend a nonrefillable probe so that there's no change of it being submerged too deep and seawater getting into it.
Epoxy bodies are good for reefers who might end up breaking them less often than glass bodies.
FWIW, most probes that I've used (typically higher end ones) usually get broken before they no longer work well (that is, they can no longer be calibrated properly ).