I would argue, as others have, that Norway became a worse and worse drag on the Germans as the war went on. I would also argue it was strategically illogical for Germany from the beginning to invade.
The thing is if the objective was to secure winter ore supplies, there was no need to act in the springtime.
Also, the western campaign was already planned, and it resulted in the capture of the Lorraine iron ore fields, rendering Swedish ore much less important.
Now it can be argued that Germany did not conceive its victory over France would be so rapid, that the 1940 offensive was meant to seize key terrain, and that German planning allowed for a war on France that might continue for many months or even into 1941.
However, I would counter argue that in any scenario where Germany fails to conquer Lorraine (which is so close to the German border) in 1940 is a scenario where Germany is doing very badly indeed.
If Germany failed to gain Lorraine by winter in theory occupation of Norway would secure winter ore, but in such circumstances Germany would need all the air and ground forces it could get to fill gaps on the western front by the winter and into 1941. Having forces strung out along the length of Norway would have been an unaffordable luxury in that case, with a high chance that the Allies could counterinvade Narvik and negate the ore shipping route anyway, rendering the whole effort a waste for Germany. Thoughts?