It's even more-so true for t.co URLs though because instead of just 1 point of failure there are 2 points of failure. The original URL may work for another decade but if you don't know what the URL is behind the t.co URL and Twitter is down or whatever, then you're just out of luck.

I don’t think it necessarily changes the reliability of the URL. A server or dns change is similarly problematic.

The only issues I have with shorteners is that they obfuscate what you’re accessing (so if it changes, it’s harder to know) and they’re a privacy issue