If you use a ceiling fan with a 72' downrod (6'), the blades are going to be at 17' above the floor.
It is most efficient to have the blades not higher than 9 feet above the floor.

Maybe it is better if you use a ceiling fan with a downbrige system instead of a rod, they are very stable. I think you can find them up to 72', too. Most of them have a more contemporary look (see link). I think they look nice as long as they do not look out of place.

How big is the living room?
If the room is very big and you like drama, maybe you can use one of those double ceiling fan for stability and proportion.
DH likes those (I am not sure if he was serious). They are not my style but perhaps you like them.

Here is a link that might be useful: {{gwi:1437282}}

thanks martha for the link, but not the look for us either. This house will be more of a farmhouse, building out in middle of a farm, so nothing contemporary. That does look like a very sturdy system though. The LR is 20x20 open floorplan. My other option is to mount two fans half way down the ceiling, because the room is large enough, but I was hoping just for one in center. All these decisions that have to be made NOW for the electrician.

I have a great room set up similar to yours. It is not cathedral but I do have a fan hanging from a long pole. It is a hunter brand and I have very little wobble. It is more of a pain to change the bulbs. I have it about 12 --13 feet above the floor.

Fanimation. Ours is great. No problems with wobble. Don't think the style is farmhouse-y, but it is certainly a conversation starter! Our room is 21' and our fan is about 14' off the floor. I've given the link below.

We have a Minka Aire in our bedroom (16' cathedral) on a 5' downrod. It does fine too.

Here is a link that might be useful: Fanimation Caruso

Dixie,
That is the one that I call a double ceiling fan.
For that height might be more appropiate so it does not look lost in the big space.
Yours is nice and I think will be ok in a farmhouse.

This is the Minka in our bedroom (Gyro in Belcaro) It's pretty cool. It rotates 360 degrees too.

Here is a link that might be useful: Minka Fan

Like most ceiling fan manufacturers, Hunter makes fans to compete at different price levels and you generally get what you pay for. IMHO your best bet is the high end Hunter in spite of your electrican's opinion.

It is not necessary to hang the fan on a very long rod to effectively move air in the room but a 3-speed fan helps. The height choice should be an aesthetic one.

Lights on the bottom of the fans light the middle of rooms leaving the walls and ceilings dark so I avoid lights mounted on fans. Hanging a fan too low can create moving shadows from recessed lights.

When lighting a high ceiling space I recommend first paying attention to lighting the walls, then task lighting, then dramatic accent lighting, then general lighting. Few electricians will understand this approach so you should map it out well in advance. Sometimes it is necessary to install a halogen up light on a wall or two to light a high ceiling. The worst place for lighting is low, dead center, and in your eyes.

Here is a link that might be useful: Hunter fan

macv, do you have a diagram or previous sample lighting plan of a large great room that you could post please? I would like to see how you would handle the lighting for a 20x20 room if possible. Thanks.

My space is similar to yours- 16x30. My ceilings are 23 foot high.
I found out 2 things about big box- HD and Lowe's- Lowe's describes the fan, the electicity used, the % of effiency online. HD does not. I thought I found the same fan (Hunter) at both stores, but when I actually looked at the ratings on the box they were not the same.
I bought 2 upper grade Hunter, put them on a 4' rod, they came with a light kit that takes candelabra sized, so I bought both CFL and regular incadescent- I could not tell any difference between the bulbs so for CFL I can run 4 bulbs for less than the price of 1 incadescent (60watt for 14 watt). They don't let you read, but put a nice gentle light in the room.
I have used both Hunter and Casablanca since 1987- I have only had a problem with one- the Casablanca.
There is no wobble with these Hunter fans.
I had electric baseboard heating installed at the same time and the fans make such a difference in pushing the rising warm air back down!
I am very happy with these fans!