Seeing as how you have a lot more experience at it than I have, I'll have to take your word for it. But I also think that whether you always go to the same place makes a difference, as does whether you have a family.
I know on my one trip (to Columbus, OH, not exactly a mecca of tourism) I had a fabulous time. I was there from late Sunday afternoon to early Saturday evening, basically having Sunday night (dinner, movies, arcade) and Saturday (science museum) to myself. But each evening we went out to dinner and even though I didn't do anything terrible exciting, I had a great time. The people who didn't seem to enjoy it as much were either people who went to Columbus all the time or people who wanted to get home to their families.
Two of my best friends at my last job were Sales Engineers (a fancy name for consultants). They traveled a lot, to a lot of different places. When I first met them they had both had several years of frequent trips and both were still enjoying the travel. Then one got married and the travel became less enjoyable and more of a hassle because she had a reason to want to be home. My other friend got switched to a big client which meant that he was traveling mostly to the same two or three places all of the time. His enjoyment level lessened as well.
I can definitely see frequent travel to the same place or few places becoming a drag in a hurry, especially if you have people waiting for you at home. I'd like to get to travel a bit while I'm still unattached
To that end, I've started spending some of my money on travel - since Jan 2000 I've been to NYC 4 times plus to Philadelphia, St. Louis, Israel, on a Caribbean cruise (Bahamas, Puerto Rico, St. Thomas/St. John), and to Amsterdam. I have a trip to San Francisco/San Jose tentatively scheduled for October, one to Vegas in November, and one to Paris in February. It'd be nicer still if someone else would foot the bill. Maybe that will only be enjoyable the first 25 times. In that case, I've got 24 to go