magazines

It would seem that keeping magazines loaded for long periods would weaken the spring and possibly cause misfires. Is their a "rule of thumb" about downloading magazines periodically to avoid such issues?

I just noticed that the elusive magazine for the model 85/86 can be found on gunbroker. The seller is offering 2, each for $125.00. These magazines are impossible to find, so if you own an 85 or 86, this might be your chance. http://www.gunbroker.com/Auction/ViewItem.aspx?Item=484781500

I am seeking 2 - 15 round .380 magazines for my Bersa Thunder 380 Plus. New or used is fine. Please let me know if you have any you are willing to part with. Thanks, Soundwich