How do open hardware devices in the sub-$250 range actually hold up on parts availability over time?

Repairability claims are easy to make at launch, but the harder question is whether the supply chain holds. For open hardware devices in this price range, how long do replacement parts stay accessible through the original vendor or third-party sources? And does having published design files or an OSHWA-certified spec actually translate to better long-term parts availability, or does that mostly matter for people willing to fabricate their own components?