Hi,

Your site is a Q&A so I presume that every time someone create a new Question it will generate a unique URL for that.
Indepentend if you have or not an answer you want Google to crawl and index your site as quick as possible to start to analyzing the new page and bring traffic to it.

The best way to expedite this "re-crawling" is to use a ping service that you can trigger after your user answer the question.

PS: If you site is updated frequently you shouldn't have a problem with crawling, because Google usually identify this type of website really quick.

Drop me a call is free for this week.
Best,