Usually before the gpu dies, the fan would die first.
Google: <GPU_Name> <algorithm> hashrate
Usually the fan will sound weird with some clicking like noise, like scratching something around the fan.
But to be honest I never came to a point when the GPU died out.
The longest card I have used and kept is about 5 to 6 years before the card replaced with another upgrade.
The longest I had running on a card is about a year with in between stopped for no more than a day before started to run again, actually 3, 4 years about and a longer break for a day to a week time.