Due to where I live, it's not easy to get seeds and growing outdoors is not pheasible. My last grow, I had a 2'x2'x5' custom veg cabinet and another 2'x2'x5' flower tent. I just had major remodeling done to the house and had to get rid of the veg cabinet.
I wanted to expand the flower area, so just went to a 4'x4'x6.5' flower tent but, as a result, had to shrink down the veg area to a small DIY veg cabinet that's only something like 30"x18"x30":
That little cabinet will need to hold four mom's plus enough clones to make sure I can flower four plants at-a-time in the new tent.
The clones will NOT be vegging long in that cabinet before going into the tent in large containers to finish vegging and flowering.
If it were easy to acquire seeds and/or I had a lot more space to work with, I'd have a different strategy.
If the bonsai's are maintained properly, there should be no significant loss in vigor or potency of the clones over time, although, the longest I've kept one is a little over 2 years and, at that time, under GLR light schedule, she started to go into flower.
Typically, after a year, or so, I just turn one of the clones into a new Bonsai mom, anyways, or start on a new strain.