You know, those cheap Broomhandles and Lugers are just beaters so go ahead and shoot the heck out of them. History tells us that what is common and cheap today will be rare and expensive tommorow. Some fun examples from my past, a Dasiy VL for $15 bucks that are now selling for $500. An old Webley in 455 that I picked up for $20 bucks that is now worth $600. The FN49's that were selling at about $80 that are now $800. The Russion Makrovs that were selling at $90 a couple of years ago that are now often in the $300 dollar range.
The point is that your Makarov will go up in value as soon as the wholesale shops run out. To that end, go and buy another while they are still reasonable in price, put one aside, and have fun with the other.
There are few guns out there that should not be used, but they are the truly rare. Some that I have owned would be the prototype guns such as the Vickers / Pederson rifle, and the S&W Light Rifle. The reason for not shooting this is if it breaks, there are no replacement parts, and so the gun will be damaged forever.
Again, I would shoot your Makarov, these are a good gun and parts are advailable. Since I am a collector, when guns like these come on the market, I do tend to buy two, one to shoot and one to keep.