Fail to plan = plan to fail.....
I have dodgy knees, so I've
got to do my homework in advance of departure for a holiday. To be honest, there's not much I want to shoot that I can't capture with my Canon F1-N, 20-35mm f3.5, 50mm f1.4 and 85mm f1.8 - but it isn't lightweight gear. My M6 TTL, 28mm f2.8, 50mm f2 and 90mm f4 is the lightest travel kit I have and it commutes to London and back with me every day.
If I have the option to get "trains, planes and automobiles", then my F5 (or D700) kit comes with me as it's AF and I love my Nikon glass better than my Canon FD.
If I'm driving my own car and I can pack what I like, the Hassy 500c/m, 40/80/150mm lenses come with me, together with a bit of light walkabout gear like that mentioned above.
My missus bought me a superb pressie for my 50th the other week. I'm now proud owner of a glass fibre legged tripod called X1-Brian from "Three Legged Thing" company. It weighs 1.5kg (including ball head), it folds to 400mm, will carry up to 8kg and is very comfortable with the Hassy 500c/m and 40mm CF FLE on board.
I have a hankering for a 5x4 but I doubt I'll ever get one.