Only takes about 100 metres to spread the oil around the hub, and then it will spin freely, 'til it gets hot. I'm talking cold, from sitting overnight!
Go out one morning, lift the bonnet, if the fan is hard to turn, leave the bonnet up, make sure you're in neutral with the handbrake on, door open, fire her up and run it constantly around ½ to ¾ revs and listen closely. You may not be able to tell when the fan is locked up, but you sure a hell will notice the quiet when it frees up and slows down.
Or, even better, get someone else to run it and stand at the side and stick your hand in where you can feel the airflow, obviously, without doing yourself damage.
Lastly, if the vehicle is not overheating and there's no oil seepage on the shaft, the fan is doing exactly what it's supposed to do, so the best thing you can do is nothing.