Maybe you noticed, maybe you didn't, but, I decided to not use valves in my coffee bags. So what is the valve for in the coffee bag you're wondering? Well it's supposed to let CO2 out of the bag when the coffee is "off gasing" which if there wasn't a valve the bag would explode...K...hasn't happened.
The valve, I believe lets all of the awesome smells from the bag and takes away the flavors...(I know for sure the smells aren't as strong; but the flavors...I don't know. But, my coffee tastes fresh even after a month sitting in the seal bag.
Now, I let my coffee beans sit in a separate container after roasting before grinding/bagging them because there actually is CO2 that leaks out and can cause the bag to expand RIGHT after roasting them...however, if they sit for 8+ hours usually they're good.
Also, another reason I don't want to use valves...EVERYONE ELSE USES THEM and to me...some coffee's stand out and taste good and others taste the same as a bag of starbucks or dunkin donuts you can buy in Krogers/Walmart/Meijer etc...
So hopefully this gives you an idea if you've wondered why my coffee bags don't have a valve on them. Now you know. So, go enjoy some coffee..or searching the interwebs for things.