Mothers: to keep or to clone?

Hey guys, Just a quick question that Google searches haven't resulted much for me.
I was talking with a friend about plants and making a plant a mother. He told me that If I grow something from seed, take clones off it. make one of the clones a new mother. Flower everything else, that each time I make a "New Mother" her generational clones will become weaker in potency, yield, quality? IS this TRUE? because I was to understand that a clone had the "EXACT" DNA of the mother. Is he correct? and what would be the best way at maintaining a small mother good for about 15-25 clones every say 90 days? Thanks in advance.

no he is not correct, you will never notice... I have buddies who are on 50+ generations and bud is still bomb every time.

Repped. ty.
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EDIT: so then Instead of making a "Mother" and maintaining it, I can in fact take the "Easy" road to motherdom and just take a bunch of cuttings, then make one a mother, flower the current "old" mother with the "Brood" of children. and never have to worry so much about anything like rootbindings or root pruning an all the headache that comes with the maintenance ? I would simply just have to do the LST training with the new mom all over right?