Water Heaters - To Flush or not

I have a 14 year old hot water tank that is working well but has never been flushed (bad me, but I am coming around on this and other things around the house). Somewhere I think I remember saying that if you get too far down the road this type of thing is better left undone rather than risk flushing 14 years worth of deposits. Any insights would be appreciated.

Having a 14 year old heater is quite a feat. I have heard of 20 year old tanks but anything over 10 is pushing it. Most of the reason for flushing and draining is energy savings. If you have a gas heater, the heat has to go through the layer of build-up to heat the water. The thicker the layer, the more gas it takes. Electric heaters use elements that are on the side so it is not as big a problem. Electric elements will collect mineral deposits after a while but not as bad as a gas heater since they lay on the bottom and obstruct the heating process.
Both type heaters have a dip tube that the incoming cold water goes through. The tube takes the cold water to the bottom and pushes the hot water through the outlet pipe. Any solids, such as debris from the house piping system or minerals usually settles on the bottom of the tank. Flushing and draining helps to remove this from the tank. Otherwise, it can go through the hot water piping and clog supply tubes, aerators and sink/shower valves.
Depending on your water conditions and house piping, you could have such a build-up that it may clog the tank drain when you try the flush and drain procedure. I am an advocate of flush and drain but in your case, I would be getting prices on a new unit. Disturbing what is in the tank may cause more problems than it solves. Good luck.