What I have a bigger issue with is bands with scarcely one remaining member or where the band is still touring where primary composer is no longer with us. Dr Feelgood is a clear example, and also acts like the Yardbirds, The Animals (without Eric Burdon), Thin Lizzy, Chickenshack, there was even a band called Taste a couple of years ago, despite Rory G passing away in 1994. Then there's the case of two Wishbone Ashes. My parents recently saw the Pacemakers, the name sounds quite apt given the age of the respective members! 
Agree, for the most part; I'll probably be seeing Dr Feelgood shortly, for the first time, but have to say its because VATA & The Mentulls are the supports - and that its in a hall very local to me. Thin Lizzy, I agree; though I'm not keen on "tribute bands", I have heard there are some better than the current Lynott-less band; however, there is word that Gorham & Co are recording, and if the product comes up to scratch, then they are still a viable band and I think then the argument should be that they change the name somehow, i.e. drop the "Thin". Deep Purple could easily be included here; only Ian Paice being original member (both times round...).
Aside from bands at the "pop" end of the spectrum - those I call the caberet toupes, the last couple of years has seen a resurgeance in 80s hair-metal bands that were scuppered by the rise of Grunge. If they've still got it on stage and can produce something worth listening to, then all well and good, but what if its a case to top up the pension plan? Do I include Van Halen here?
The irony is that many of these acts are still able to command festival slots at events such as Cambridge and Skegness, to the detriment of new acts. In my view the acts in my second paragraph lack credibility. Having said that I will be seeing Powell's Wishbone Ash tonight as the Mentulls are supporting them, and I've not seen them yet.
One thing I am unsure about is how beneficial touring with the likes of Ash or Robin Trower is for younger acts, as it seems to be placing them in the wrong audience demographic.
Yeah, but have you not noticed, when going to see these bands, certainly the majority of the audience is we "mature" persons, often with offspring in tow...(willing or otherwise is debateable) and this "second generation" hopefully, will pick up on the younger support. As a case in point, I'd cite the recent Rival Sons tour; sure Classic Rock did a lot to promote the band, but outside the High Voltage Festival, they toured here with Judas Priest, hardly spring-chickens, a couple of times, until this year they headlined themselves. At the Newcastle gig, more than half the audience were under 30. I suppose another thing to consider, in these money-tight times, are venues and promoters more apt to take a chance on an "established" name over a relative unknown? Don't knock the power of nostalgia, which brings me back to the point of the second generation being dragged along.
Trying to bring things back to Curby's original issue; there are still a lot of bands that I'd still like to see, Rush, The Cure, that some would call "veterans" but does that make them obsolete? Simply, there are always going to be 3 basic camps:- die hard fans who see no wrong: those who think they (bands) are past their best and should hang up the toupe and corsets: and those still curious to see the act. That said, I supose you could say that along with The Beatles, ABBA are an act who "retired" with credability intact.
Just a few thoughts.
Mike