How much is a 2-year old laptop worth? Because if you buy a new laptop every two years and don't even sell the old one, you're only spending $500 a year, which is less than you are now.

You really shouldn't trade-in your laptop on the basis of trying to maximise its trade-in value, that doesn't make economic sense.

You should be incentivised by trying to minimise depreciation. You incur the greatest amount of depreciation closest to the date of purchase, so the longer you go between purchases, the less depreciation you'll realise.

If I expected to say get, $450 after 1 year, and $250 after 2 years. By trading in every 2 years, I'm getting a laptop that's a bit older, but you're also saving $14.58/month on depreciation. If the year after that becomes $150, you'd be saving $22.22/month. If the price is worth it is subjective, I'm just saying going for maximal trade in value doesn't really make sense, since you save more money the lower the trade-in value you get.