I think that most artists from the 60s need to hang it up. There are exceptions but many of these artists are embarrassing themselves. I guess they're well insulated from anyone who would tell them that it's over.
An interesting observation about Van and many other artists from the UK is that they were able to absorb and adapt American Blues and R&B remarkably well, but few were able to do the same with American country music, when country would seem to be the more straightforward, less difficult genre to absorb. Much classic country music has its roots in folk music from the UK too.