I’m doing the same. The real problem is telling apart flakey or temporarily down relays from ones that are actually dead. E.g, if I treat “fail to connect during startup” as dead, I risk missing relays that are just temporarily offline, which can be catastrophic for long-running processes like relays. But if I don’t, then I need increasingly complex retry algorithms (“penalty box”, exponential backoff, etc.), which still wastes time and resources retesting truly dead relays. Even worse, some dead relays just hang connections. Right now I’m using a 5-second timeout when testing relays, and even that adds up quickly when combined with retry algorithms across thousands of relays. A good blacklist would be very useful.