11 years on my indica, 4 years on my sativa. Pull clones twice then into the budroom. I am acquainted with a grower doing his 15th year on a hybrid.
I have never understood this degeneration theory, I have never spoken with anyone with direct knowledge, everyone always "heard" it somewhere else.
ievolution, do you have any details on what the plant fail is? What parts mutated and are growing different? This is new to me and growers in my area.