How 2 Fix Videos
The job of the control arm is very important, and one of the most overlooked part of any car or truck. If you drive a new vehicle it feels tight, meaning it go's where you steer it and dose not wader around the road. But if you drive a car with miles on it it dose not feel as tight and dose not steer as good as when it was new. Two things will wear out control arm bushings one is miles and the other is just age. You can have a  older car with low miles on it and still have bad bushings. You have to think how many times the control arm go's up and down when you are driving. A lot of people never think about this we replace are shocks. All cars and trucks come with rubber bushings and rubber gets hard, cracks and dose not flex as good. 

If you have struts it is very common to buy the hole arm. It saves time on replacing the bushings. Most shops will just buy the hole arm. To buy just the bushings is much cheaper but more time consuming to replace. If you want polyurethane bushings you will most likely have to get just the bushings and press them in the arm.
I like the Energy Suspension  polyurethane bushings, but I would not put them on a luxury car or something that you want to have a smooth ride. The polyurethane bushings will make it a firmer ride or harder. This can be good for sport car or trucks and can help with handling. I have almost 500,000 miles on my 01 Dodge ram and it go's down the road straight and feels tight. I have replaced the control arm bushings three times. I use  polyurethane bushings because it is a truck and I am not interested in a smooth ride. I think the polyurethane bushings last longer.
You can't see the control arm bushings and when you get a front end alignment it is hard to tell if their bad or not. It is easy to tell if tie rods are wore out because the wheel will move back and forth. If the ball joints are bad the wheel will move up and down. The control arm bushing just move or flex a little it will not feel as tight. So when do you replace them. I think it should be done as a maintenance. If your car or truck has 100,000 miles on it or is 8 – 10 years old you will notice the difference if you replace them. Of course the rest of the front end has to be in good shape.
Understanding control arm bushing

If you can do the work yourself it does not cost much money. But you have to be careful what you buy, If you buy cheaply made they will not last. If you have springs, I have seen the hole control arm for sale with new bushings but I think it is a waste of money unless it is bent or something like this. The bushings are pressed in but if you don't have a press take a look at my videos to see how to replace them with out a press.
Things to remember, you will with most cars need a front end alignment and you should get one anyway. Most car and trucks have a way they have to be torque. If you torque the bolts with with the tire off the ground it will twist the bushing when you put the weight of the car back on it. Buy quality parts, this dose not mean the most expensive but sometimes you get what you pay for. This is a low cost repair you can do yourself and make your car or truck ride like new.