Many people stay for a few hours. I know at least 3 forum member who will spend 4 or more hours at the range and there are non ingo members who spend a lot of time at the range.
The 10 visit pass also never expires, so even if you only shoot once per year, you can use the pass until it is punched out. We have had folks with 10 visits that were from 2003. You can also use it for more than one person.
That is a great point. A $75 card never expires, a $75 club membership expires in a year.