I really think it depends on the person, and the requirements. Honestly, some people have a lot of CTs, but do a good job of managing them all. I am on 6, and as long as my mojo is there, I have no problems doing the LOs that are required.
I'm with Jac, I was scrapping this much anyway, so it hasn't been any extra work for me. I try to do a page at least every day, though the past few days, it's been so stankin hot, I haven't had any energy to move, never mind think LOL
ETA that if I were on a store team, I'm sure I would have to re-evaluate what I was doing, there'd be no way I could handle more than 6 CTs AND a store CT. Last fall I was on 5 teams, and when I was bombed at work, I had to reevaluate and resign from 3 of them. If I can't give what I need to my teams, I will resign from them to give someone else with more time, the opportunity.
ETA again: Now that I'm on the CTs I was buying and scrapping with anyway, it makes life easier all around LOL. I was scrapping with it anyway!