i grow norway spruce and nordman fir but im growing them to cut them at xmas.
yours is slightly different.do you mean the blue douglas fir called pseudotsuga menziesii.because this one accourding to the rhs book grows to 100ft(30m)high and75ft(22.5m)wide.so i would keep that one in a pot,maybe a bit bigger one though.

Plant it in a forest!! These are eventually huge (and will you want the hassle of removing it later when it is huge?). In my opinion they are only garden worthy if you garden is huge.

we kept one in a pot for quite a number of years before it was planted out, we used to put lights on it near the house at christmas-- we eventually planted it out and now a ladder isn't big enough to reach the top! so if you want to keep it for a few years use a larger plastic pot and a soil based compost, then put it in another larger pot (fancy if you wish) then you will find that you can protect the roots against frost make sure that it is in light shade and that it is kept moist, I even spray it all over in the summer , and re pot as nessesary. but there will come a time when you will have to plant it out

Thanks guys....
Pamg -Do you mean use the potted plant inside a larger one in the winter?