Tinkerbell shows up in a lot of different cartoons on TV now and then and has done so for many years. She has not aged a day either so I guess that means than Kes will live for almost an eternity too.
Unfortunately, that's not irony and you don't know your Tinkerbell well enough to remember she was a Judas. She sold out Peter Pan, Wendy and all the Lost Boys to Capt Hook.
The irony is the fact that Kes looks like Tinkerbell, a character that never grows up and will never die but yet Kes will grow old and die over a short period of time. Kes looks like Tinkerbell but is mentally Wendy, Peter Pan's love that didn't want to be young forever and left Neverneverland to grow old and have the life she never could with Peter. Ocampa was Kes' Neverneverland. The fact that she was facing her death in "Fury", it's natural she'd want to return to the place of her youth.
Somehow I do get the impression that you really dislike Kes because you're always trying to find something negative about the character, even when there's nothing negative to be found.
When you mentioned Tinkerbell, I immediately thought of the Disney character who is always nice and friendly and looks the same today as she did when they started to make cartoons in the 1930:s or so.
Kes is no Judas. She was always loyal to the Voyager crew.
Kes is not Wendy either, the fact that she left Ocampa had nothing to do with aging or not.
And Kes is no insane monster either as those in charge tried to make it look in "Fury" with that pathetic creature which showed up there.