How to tell if your cartridge is worn out? ADC XLM mk2

As the title says - what are the symptoms that a cartridge needs to be retired? The cartridge in question is an ADC XLM MkII that I've been using for a few years, but it's definitely old and probably saw use (unsure how much) before I got it. It just sounds... flat. It's one of those things that you don't notice until it gets to a point where you think, hmm, that isn't right.

Dip in and out HERE