The longer the stem is when you start a cutting, the smaller its rosette will be and the shorter the lifespan of the resulting plant. Those features of Echeveria aging relating to stem length are true for the entire genus, to one degree or another. And the more buried succulence, the greater the risk of rot. It's not a guarantee of a bad outcome, it's a relative risk and it's different for each plant.
As for the existing roots, here's my view. A cutting will typically root and start growing again in 6-8 weeks here. If waiting two months is the price for minimizing the risk due to buried succulence, that's something I'll gladly pay. But to each his/her own, of course.