I'm the same as doc, i make a starter from the original, split it into 6 stubbies, then make a starter from one of the stubbies, (or if im brewing, use half the original starter) then when the stubby stocks run low, the next one i brew a make a 2L starter and break about a litre into a few stubs.. i think im on my third generation, still all good..
The last yeast i did however (calf ale V) i made the 'mega starter' and dumped 5L into my crippler, and 2L into a starter thats ready to go for tonight (i'll drop in some sugar to get it active again, but its got nearly an inch of flocc'd yeast in the bottom of a 2L coke bottle) and bottled a 6 pack of stubbies..