Answer: I think it's more a factor of when the tree was cut, how far it was transported, how long it's been in the tree lot, and conditions in the home environment (drafts from heating units for example). You can help by making a fresh cut before putting the tree in its stand (most tree lots will do this for you if you ask) and ensuring that it always has water in the stand. Keep out of direct sun and away from heating units. Having said all that, in my experience, Norway pines seem to hold their needles a little longer than spruce, but I don't have any "science" to back that up!
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