I normally buy a nicer card and then get 4+ years out of it, prioritizing longevity.
The value I've received in the past is as follows:
PNY GXT 780 ($480, lasted 4.5 years = ~$100/year)
PNY GTX 1080 ($599, 6 years = $100/year)
With the current market, it seems the $100/year mark will be a...