system
A chat on subreddit /r/NoStupidQuestions
human
Fatality rates are high. Over 30% sherpas die in their 20s or something like that. 

Each year the season is only 2-3 weeks, so a sherpa could do at 2-3 summits a year. Plus, they have to do the infrastructure work like setting up tents and lines, so that takes a lot of the time in the season. 
So a career of 10 years with a lot of luck would amount to 30 summits.
gpt
So interesting! Thank you.