It isn't just a matter of heavy vs light cameras as you age.
To a large extent, it also becomes a matter of mental maturity, of eventually knowing what works and what doesn't.
Like others here have, I, too, wandered parts of the world, poor shoulder laden with either three Nikons and at least seven lenses or two 'blads and three lenses. I was younger, but also had a real requirment: work. Then, I had to be capable of attempting a wide range of images on any single assignment, so all that I owned of the format that was relevant had to travel with me.
Today, I'm not young, neither do I have photographic responsibilities. Today I am just another amateur going about the business of perhaps finding a single picture worth spending time on at the computer.
So, does it make sense to cart around a load of stuff that prevents me from going to the loo should I need to, simply because there's nobody around to keep an eye on my junk as I use the washroom? Am I likey to want to shoot something happening a hundred yards away from me – if I can't even tell what that might be? No.
Freedom of mind is an essential part of creativity.
Putting a single camera/lens combination over your shoulder as you leave the house is the answer to pretty much everything: it frees the mind to concentrate in one direction, which is really what concentration implies.
Travel simple; free your eye. If even one camera/lens is too much, then it may be time to think again and do something else. As I wrote elsewhere in LuLa, you can find a helluva lot to shoot just at home, if you but look for it. If you can't see it there, what makes you imagine that you'll see it somewhere else? Your old slr/dslr can give you all you ever need if your stuff just ends up on the web. Why impoverish yourself buying loads of obsolescent junk?
In the end, you can't buy yourself great vision.
