This is an area where I'm still pretty new, so take what I say accordingly. BTW, I've never heard of the seeded mother technique. That's very interesting, I'll have to ask my buddy about that.
Anyhows, I think you can go for many years from clone to clone as long as the plants are super healthy and only clones from healthy plants are taken. Diseased plants should be culled, etc. The important thing about clones is that they are the age of the mother plant when you take them. A six month old plant isn't quite the same as a 3 week old plant. I think the younger ones root better....but maybe that's just me.
So, anyways, I don't think you're really getting a genetic shift....more like just plants that reflect the mother's age and health....which goes down over time. At this point, a weak cutting is taken from the declining mother plant and the new mom is that much weaker, etc.
That doesn't seem to happen with teen moms.
However, I still prefer to grow by seed, and I'm excited for a new seed run coming online very soon, as soon as I can sex them and harvest some others out of the way. Then I think I"ll take a break from this clone madness and do some seed grows.