Sick tomatoes: yellow/purple leaves?

Well they're poking out the roof vents at this point, so yes I do chop off at the top to stop things getting too tangled etc (this weekend probably). Otherwise I leave pretty much alone and they're fine. I've seen arguments rage back and forth on pruning/not pruning in general (suckers etc) so in the end I've taken the easier route and it works OK. That's not to say I might possibly end up with more toms if I did prune, I don't know - all I do know is I get plenty each day anyway with no work (they're caged so support themselves), and that's good enough for me. The growing season with some/all these varieties is much the same as for you: I think they'd carry on into the following year if it didn't get too cold. None of them are that triffid-like though, which obviously helps.