Prince was 5 years old when I got him and I had him neutered about a month later.
When I first got him he marked EVERYTHING. Mostly outside, but sometimes inside too. He doesn't do it inside anymore and he doesn't have to mark absolutely every square inch of the yard every time he goes outside anymore. He still has to mark where Angel pees outside.
I'm not sure how much is behavior changed due to being neutered and how much it changed because he is used to the house, people, cats, etc. at his "new home" now.
On a side note, my parents' 13 year old Yorkie started lifting his leg shortly after I got Prince. Apparently Prince is teaching him to play, howl and pee
