If you can move them around there is no doubt it is beneficial. But for many that isn't possible due to limited space. As long as you re-amend the soil well, especially if you add in fresh compost, then no I don't think it is 'necessary'.

Dave

Thanks Dave, I was hoping you would see this post. I am adding a lot of compost to the beds as they settled about 4" and I filled them back to the top of the beds and worked them in together.

Agree with Dave. My growing season goes from April thru October, so I have time for two summer crops per year, plus one crop through the winter. I assign each of my raised beds one crop family per year (beans, cucs, tomatoes, etc) and then plant two crops from the same family in it. The following spring I rotate. I rotate my winter crops on a yearly basis too. They go into the summer beds at the end of the season, but I rotate them (brassicas, roots, etc.) from year to year as well. I have had these raised beds for four years. So far, so good.