First I've heard of this....
Like you need something else to do
http://www.azom.com/article.aspx?ArticleID=9547
Will it affect accuracy? Will your bullet lube soften and find it's way into the powder?
Oh and for the record.
When I thought I was going to get into CMP service pistol I bought 5000 rounds of 45cap ball.
Oldest sealed can was dated 1919
With the newest being 1952 it all went bang and when I was shooting well found the black bull.
I think unless your skills are into the 95%+ range you might find some accuracy loss with OLD ammo.
For the most part smokeless powder is some pretty stable stuff.
Aliant powder company was reported testing a lot of red dot produced 100 years ago. From what I remember the last round of testing they reported only a minor loss of consistent ignition and burn efficiency. Then stopped the program.
So ammo loaded correctly and stored in a stable environment with out water intrusion should be fine for a very very long time.
Now if I was needing 1/4 moa I might make fresh ammo more often BUT just the change in powder form lot to lot can be enough to make your last great load not so great...
This is the advice I heard the most and has rang true so far.
Spend more time shooting and practicing your fundamentals before working your self silly on ammo accuracy.
Point being. I know a 86 year old man who will plunk down with his JCG match legal M1 and surplus M2 ammo and out shoot many on the line with "match loads".