What To Expect From An Ageing Black Widow Tetra?

[bumbleweasle]

Aloha.. my single black widow tetra (who is single because he was rescued & I do not keep BWTs normally) is over 6 yrs old. I googled their life-expectancy & got results varying between 3 & 5 yrs in captivity/aquarium settings. Can anyone say if this is true? That would make him pretty elderly, eh? So if that's right, then what can I expect from this ageing fish? Will he get ill, or become less able to swim/eat/etc.?

(If the expectancy is wrong, say longer, then I'll see if I can get him rehomed with other BWTs.)