If what you have done in the past is working, I wouldn't recommend a change just because everyone else is doing it.
It really boils down to the cows BCS. If there are many animals below a 5, you might benefit from supplementing some grain, and/or protein. We use a couple methods on our operation. One is to supplement their grass hay with some alfalfa. We generally give 5# /hd/day. This will give the cows approximately 1 lb of protein. This will help in digestibility of the grass hay. Want to be careful, however, as overfeeding protein can really crank up a feed bill!!
Depending on your location, I would strongly recommend feeding some dried distillers grains to your cows. With the boom in the ethanol industry, we have the ability to purchase DDG grains at a reasonable price. One thing to watch out for is the calcium level. Feeding more than 3 lbs of DDG/day throws the cow's Ca
ratio out of whack. We started feeding 2 lbs of DDG to our cows a few weeks before calving. This gives them supplemental protein and an incredible amount of energy, and it is also slowly degradable so it doesn't counteract with the hay digestibility.
We have had a very rough winter this year since early in December. Many of our cows were thin prior to calving, and we knew we needed to do something. The DDG's have really put the flesh back on the cows to where it needs to be, and there also appear to be some other benefits. The calves seem to be very vigorous and lively at birth, very strong.