I just phoned Moen at 1-800-321-6636 in the USA and 1-800-465-0279 in Canada to get my information straight from the horse's mouth and so people can confirm what I'm saying is correct.
1. Moen has not installed brass cartridges (the Moen 1200 cartridge) in their single lever faucets since 1987.
Sometimes it's easy to draw the wrong conclusion from your observations. My guess would be that the Moen faucets sold at the plumbing wholesaler that still had brass cartridges were simply older stock. It's not that Moen put brass cartridges in the faucets going to the wholesaler simply because they had a policy of providing better quality product to the plumbing wholesalers. Stores like Home Depot and Lowes have much higher sales than plumbing wholesalers, and so they'd normally be expected to carry newer stock.
2. Every Moen faucet is guaranteed for life against leaks and factory defects. So, if the faucet leaks, then just phone Moen (at the numbers above), give them the model number of your faucet, and they will send you a brand spanking new cartridge for it. That cartridge will come with instructions on how to replace the cartridge. However, officially that guarantee only applies to the original purchaser, but Moen isn't sticky about that, and they'll send out a new cartridge to anyone who needs one to fix their Moen faucet.
Moen also makes the 1225 cartridge available for sale because no one wants to do without their kitchen and bathroom sink faucets while they're waiting for the replacement to come in the mail. So, if Jimbo was selling dozens of 1225 cartridges a week, then I expect the reason was because the store was selling a hundred Moen single lever cartridges a week. Either that, or people would prefer to just pay the $10 for the replacement cartridge rather than wait a week for a replacement to come in the mail.
3. Moen is now changing their production to eliminate the 1225 cartridge. All new Moen single lever cartridges will now come with the Moen 1255 ceramic cartridge. The way to tell if the faucet has the new ceramic cartridge is by the supply lines attached to the faucet. If the supply lines are solid copper, it will have the 1225 cartridge. If they're braided stainless steel wire supply lines, they will have the new 1255 ceramic cartridge.
The new Moen 1255 "Duralast" ceramic disk cartridge will replace the 1225 cartridge.
Moen 1225 cartridges last a very long time, not six months to a year. If they only lasted six months to a year, then in a building like mine with 21 apartments and a total of 63 faucets (kitchen, bath sink and T&S), then one could reasonably expect to be replacing 63 to 106 cartridges a year, or about 7 or 8 per month. I don't do the same repair 7 or 8 times a year in my building on anything, let alone 7 or 8 times a month. Even a rubber washer will last many years. No plumber would have any respect for any faucet that had to be repaired every six months to a year. And, of course, if Moen faucet cartridges had to be replaced every 6 to 12 months, Moen sure wouldn't enjoy any brand loyalty. But, the fact that they're probably the most popular faucet on the continent means that either all of us are stupid, or that they make decent products that do stand up well.
"Even though Nestor still can't seem to get it..."
What's with the attitude?
I figured I strive to "get it", so I phoned the sales agents for Moen. I phoned RNG Marketing at 1-877-280-6628 in Regina, Saskatchewan and talked to Justin Grohs who has represented Moen for over 10 years. During that time, he would have had dealings with plumbers, retailers and end customers regarding pretty well every product Moen has made. He told me that he has no personal knowledge of Moen ever using a porcelain anything inside the brass body of their faucets, and has never heard anyone make any reference to there being anything porcelain inside any Moen faucet. So, with respect, I think you're just making all this up. If you have the model number of the faucet, post it, and I will phone Moen personally to see if that model of faucet had a porcelain flow restrictor in the body of the faucet that would render the faucet useless if removed.