I do 2000iu a day, winter or summer, and I try to get as much sun exposure as possible. I figure if I am getting the CLO vit. D, then my body will simply make less (if it needs to) from the sun exposure. The body is smart that way.
I'm yet to see someone OD on vitamin D from CLO. As long as people don't go crazy with it, I don't see much of a problem (in my practice or from the literature). 2000iu is not going nuts at all, IMO.
People get toxic from synthetic D3 all the time. I stay far away from that stuff.