> they couldn't care less if you're gone the next day and forget about you completely the day after

This is a lesson I wish I learnt earlier.

I quit thinking I was irreplaceable based on the sheer urgent firefighting load they put on me. Once I quit, never heard from them again. All those urgent tasks that somehow only I got assigned "because there's nobody else", suddenly managed to get done by someone else or nobody because they weren't actually urgent.

"If you want something done, give it to a busy person" - Benjamin Franklin

I was even the “lead” at a SaaS in daily firefighting mode and pushing new features out quickly on a team of three engineers and one half-time one. I was 99% sure they’d go down the next day I left but somehow they kept on trucking. We’re all replaceable whether we like to think it or not