If you read the FAQ on the Wolff (Gunspring) site, you get a slightly different story. As the cited article suggests, when you push springs too far, problems can occur. But the Beretta rep quoted didn't address some of the increasingly common events in magazine usage.
This is from the WOLFF FAQ section:
http://www.gunsprings.com/faq#Faq5
Magazine design and capacity also affect the longevity of the spring. In many older pistol designs, maximum capacity was not the always the goal such as with the 7 round 1911 Colt magazines will last for years fully loaded. There was room for more spring material in these guns which reduces overall stress and increases the usable life of the spring.
More recently higher capacity magazine have become popular. These are designed to hold more rounds with less spring material often in the same space. This puts more stress on the spring and will cause it to fatigue at a faster rate. Unloading these magazines a round or two will help the life of the spring. Rotating fully loaded magazines will also help the problem somewhat but it is not always practical.
I'm a big CZ fan. I've had a bunch of them. Witnesses, too. And other clones. Back during the mag ban period all you could get were the 10-round mags (unless you were lucky and stumbled on some pre-bans.) The 10-round mags seem to run forever, but the 15 (and now, 16, and 17) round mags seem to do less well. Why? Well, for one thing, the
10 and 15 (and 16) round mags use the same springs... Could it be that the higher capacity mags are pushing springs past their limit?
Rotating mags doesn't save springs -- it just spreads the wear out over more mags over a longer period. Why not just use a couple, and replace the springs more regularly? (Seems like a trade off, actually.)
Until I hear from somebody with good metallurgy credentials, who works with springs, I'll pay more attention to folks at Wolff on this topic than anyone else.