Oh yes, the perennial question.
It really does depend on what you think you will be photographing and how close you think you are likely to get to your subject, as to whether you start packing long lenses which take up space & weight.
I have become a fan of the minimalist approach, although my version of minimalist and yours could differ greatly.
If I was doing an oseas city orientated trip I would be packing my K20D, DA 21, FA 43 & DFA 100 in my Delsey shoulder bag, along with my Gitzo light weight monopod with its own ball head (doubles up as a very handy walking pole).
My wife would be packing her K200D & Pentax 17-70.
The only other lens I might consider would be the Tamron 70-300, but then I would probably leave the DFA 100 home (but I love that f2.8 in tricky light). The advantage of this is that
if the better half & I can work as team, then we cover 17-300, with the 43 in the pocket for low light. But each sees things differently so some opportunities are missed with this approach.
As I said, the perennial question.
Good luck with it
Grant