I've discovered a thing or two about traveling over the years. In my experience, every trip ends up feeling like it was just the perfect length. I think that as you mentally prepare for a trip, you keep in mind how long you will be away so that as your travels are coming to an end you feel ready to go home. I used to be baffled at how a mere week long journey could wear me out when I once backpacked for six weeks, never staying in one place more than a couple nights, and managed just fine. It's all in what you're expecting going into it. You'll bring as much mental and physical energy along as is necessary.
However, this theory of mine was completely blown away this past week. I spent ten days trekking around England and Scotland. I of course knew ahead of time it would be ten days, and I prepared accordingly. I may have been running low on socks and underwear by the end, but I had no other indication that the trip should have been coming to an end. I wasn't homesick (for either Spain or the U.S.); I wasn't craving my own bed yet, and I was by no means done yet.
I may have fallen completely and utterly in love with Great Britain, its lush greenness, and its fascinating history. More detailed posts will come later, but here's a taste of what got me hooked. Let's just say I have never been more determined to revisit a place and dig into it deeper.