Yeah, I think my first laptop lasted... six years or so before I needed to replace it? But at that point I was pretty much just typing up Word documents and occasional emails.

Now, I do quite a lot of digital art, among other things, which involves some massive files for a computer to handle. So I do expect to need to upgrade more often, in order to keep up with more recent heavy-duty programs and such. But I still hope to have them last about four years before needing to be replaced. (For a desktop it'd be longer, of course, but I really need the portability of a laptop.)