Well I tried it, and I think I got really burned out on Z2... Heck I even got ovvereached some since I started having issues sleeping and had to take a week off. I don't have an issue doing Z2 on my 'ez' days or in some part of a long weekend ride (which will be all mixed up zone wise anyway) - but being a CAT5 with a long way to go I will stick with SST being my easiest 'hard day' for now. If I had to do Z2 every day for 2+ hours again like I was doing I would throw my bike off a cliff. Not going there again for a while at least- although I see value in doing it as a short 'base cycle' to change out from high end work for a few weeks or something. I will probably revisit this next year after more racing and miles on the legs. - Im only doing 20 /30 min crits anyway, maybe a few TT (20K) for fun.