I've read somewhere, that every 10°C above 80°C will decrease your graphic cards lifetime twice.

So if it 10 years normally:
- 90°C will make your VGA's lifetime 5 years
- 100°C — 2 year and 6 months
- 110°C — 1 year and 3 months
- 120°C — 6.5 months
- etc.