I did that for a while. I had a 2010 MBP I thought I would use for a while, (Even installed an SSD in it) but a year later I decided it was too heavy and too much so I replaced it with a MacBook Air because of its all-flash design and higher resolution. But then a year later I once again replaced it with another Air with more speed and twice the RAM and SSD because I got such low specs the year before. And I figured I'd keep it for a while too, but I felt it was too slow and realized I was constantly upgrading every year spending too much. So I decided with my next machine, which I bought a year after that Air (2013) I was going to make sure I go as high spec as possible. So I got myself the 15" Retina MacBook Pro with the dGPU, a nice 512GB SSD (Which is more than I need) and the 16GB RAM. I ordered it and picked it up at an Apple Store. I'm still using it now. I didn't get AppleCare and I am regretting it because my keyboard is fucked up. I'm using an external BT keyboard on top of the built-in keyboard with the topcase keyboard .kext disabled until I can afford to get it fixed. But I plan on keeping this machine for at least one more year if I can save up the money in time at which point I will decide what to get that suits my needs at the time. I got the top of the line Pro because I wanted to be able to play games and run Windows with games inside it. But my current plan is to get a gaming PC for games and possibly go lower next time. Probably a 256GB SSD, still 16GB RAM, but possibly 13". I won't know until the time comes. So I'm hoping for next years update to work out the kinks. And by then the Touchbar will be completely figured out and everyone will be using it. And hopefully they'll have also figured out the pricing by then too. Because come on, seriously.
Bottom line, from now on I plan for getting at least 3 years out of any machine I buy