Leaks are a big warning sign
A disposal leaking from the body of the unit is often near the end of its life. A loose connection can sometimes be corrected, but a cracked or corroded unit usually needs replacement.
Humming without grinding
If the unit hums but does not grind, it may be jammed or the motor may be failing. Older units with repeat issues are often better replaced than chased with temporary fixes.
Age and repeated resets matter
If your disposal is older, smells bad, needs constant resets, or keeps tripping power, replacing it can be the cleaner and more predictable choice.