In my experience, it does not weaken the springs. W.C. Wolff of Wolff Gun Springs (www.gunsprings.com) advises that so long as the spring is not compressed more than it's designed for, being compressed to that degree does not weaken it. He goes on to say that what "wears them out" is being used, i.e., compressed and then not compressed as would be the case in a pistol's mainspring when the gun is being fired and in a magazine as it's loaded and then emptied. In over 30 years of shooting Hi Powers, I have not had to replace the original mainspring in any of my Hi Powers. I have replaced perhaps two magazine springs.
The same has held true with any and all quality semiautomatic pistols I've owned over many years. I truly believe it is a "non-issue".