Pre Qualified vs. Pre-Approved

[Elliott Wolf]

Another newbie question...

So I read this article ... 

https://www.biggerpockets.com/blog/pre-approval-vs-pre-qualifying

I understand that pre-approval is key to make sure you secure the house you really want if it comes onto the market, because surely other people will want it to. 

My question is how good is a pre-approval valid for? Is there a time limit you must close a property after you get pre-approval?

Any help is appreciated. Thanks!