Soy milk expiration dates- myth or reality or marketing ploy

I usually buy soy milk in the 64 ounce container- I notice on most brands that it states the product should be consumed within 7 days of being opened- I only use it in my breakfast cereal so one of these containers can last me about 3 weeks.

I've gone well beyond 7 days after opening and have not noticed any souring, decline in quality, etc...

And I'm still here to write this!!!!!! Is this a ruse to get us to buy the product more frequently?
Am I putting my life at risk????