A lot of rifles get bought, shot a few times and then sit for years between use by each consecutive new owner. For them the 1K test is a valid test as they're unlikely to surpass it. You're right though in that it doesn't tell much about the long term durability of that rifle seeing some hard use and high round count.
When I went through a training program years ago, the AK was a large block of instruction.........that and other Soviet weaponry, but the AK predominantly. The published life span of the AK varies greatly, depending on country. For example, the T56, Chinese variant, has a published life span of 6000 rounds. This figure is based upon use, but is an average figure, using bimetal jacketed rounds, corrosive primers, and on full auto................with no maintainence, under combat conditions. This was the average figure, published by the Chinese government, before their would be a breakage or failure of a part......which part, was not told that. This is the kind of reliability we are talking about.
Now, in this Country (USA), we clean our stuff, generally, and dont typically have full auto, or typically corrosive ammo. So judging by my past experience, the AK rifle should last well into the 15000k mark with good maintenance and lube, assuming the proper materials are used, and semi properly put together.
Ron from the Las Vegas gun range Battlefield Vegas, where, like many Vegas range’s they only allow their rental guns to be used, shared some thoughts on how different AK rifles fail after tens after thousands of rounds (the above photo shows 30 days worth of 7.62x39mm steel shot at their range...