I am thinking about 3 or 4. The situation is that the Accidental Damage Protection option is gone once you stepped up from 3 to 4 years Onsite. I asked the chat agent and he offered me an additional year of Onsite and ADP at about $100 more.
It depends on the fan noise. If it is tolerable, then I may keep it for about 5 years. If it is still noisy, maybe 3 years. I can't tell until I have tried the machine. However, I think it is cheaper to purchase the warranty with the machine at the same time. Of course if I get a good job, I change every two years.