I have been grinding organic hard red winter and spring whole wheat berries off and on for over 30 years. I have never had that taste. But buying flours off the shelf in markets I have had it plenty of times. It could be rancid. The bitter taste is charactoristic of rancidity. This is usually accompanied with a slight burning taste after swallowing. I usually taste the raw flour after grinding to check for that. I had to throw away several batches of just baked corn bread from store mixes that I didn't taste before hand. It's an unmistakable taste even after cooking. A few bags of ww flour have been rancid as well. Most people don't use that much whole wheat flour so it sits around in the store too long.
Ron
That bitter taste is why so many people say they don't like WW,,,,,
At least that's why I didn't like it until I milled my own WW, I think there is no comparison. qahtan
The wheat berry in its whole form will keep for years and years so long as its kept cool and dry. If they get wet, they sprout. Otherwise, though, you really don't need to worry about it. I think it's one of the big advantages of home grinding for those who bake a lot of flour with whole grain flour -- you can buy in bulk to save money and not worry about that 50 lb bag going rancid.
Personally, I'd not store whole wheat flour for longer than 6 months, and I'd store it in the freezer, but that's just me. Lots of information on storing wheat berries in the home here, too.
Frankly, some of the storage advice seems a bit of overkill to me, though. I just empty a 50 lb bag into two five-gallon buckets fixed with Gamma seals, and leave it in my garage. But then, I usually go through 150-200 lbs of wheat each year, which means I'm done with a 50 lb bag in 3-4 months. But I bake all our baked goods from freshly milled flour -- English muffins, pancakes, waffles, brownies, cakes, pie crusts, bread, etc -- and I also bake a lot of bread to give away as gifts.