how long does it take for a question to be deleted from Yahoo...some I see for months?

They are not unless violating user agreement. They stay until voting a best answer then moved to the 'discover' posts.

The scope of YA is a site where people can learn by asking questions.

Sadly, the lack of community policing, moderation, and changes have the site infested with abuse.

Wasn't always like it is now. Been here over 10 years and seen the changes.

Questions are open forever and can continue to receive answers even after a best answer has been chosen.

Never.

The whole reason for YA existing was to create digital database of knowledge seeking questions and answers.. Yahoo And Verizon does NOT delete questions after a certain amount of time. Question that get NO answers for 7 days are deleted automatically by house keeping programs, But if people DO NOT report the questions, THEY STAY and are accessible FOR YEARS.. YA is 12 almost 12 years old.. So some of those questions really are that old. A couple of months more or less does not matter to computer network system. YA is run by server computers and computer programs, NOT Yahoo or Verizon staff. Yahoo and Veerizon staff DO NOT answer the questions on YA.

it depends how many people flagged it