And I bet those SFP+'s overheat all the time too. The reason _why_ the big guys i.e being finisar don't make ER SFP+ modules is due to the heat.
if you look at the XFP's and the distance it frankly sucks and isn't a full cwdm spectrum. look at the dwdm xfp er zr and 120km these are just your normal standard xfp optics that fit into a cwdm mux nothing different from what I mentioned above.
The other ones are modified LR and ER optics which all have differen distances on them. You really have to be careful with the power per optic while putting it into a mux.
I wouldn't touch these optics if your going to do it make sure they are all the same power and not all over the board.
Well, the guy who asked the original question only needs 4x10G at 1000 feet distance. So a passive cwdm with 4x colored XFPs might work very well for him. Of course if you need something long distance you wouldn't go this route.
About the long distance SFP+ - i don't know how they can pull this, i think the SFP+ specification doesn't provide enough power for this to work reliably, plus it would need software support from the router/switch, so SFP+ for anything non-standart would probably be big headache. But XFPs don't have this problem. Not that i have tried these CWDM XFPs myself, just sharing my thoughts