Depends on terrain!
I like my stand locations up high (like on a ridge) and my feed locations down low (like in a valley)! On this lease I have 3 stands and they are all about 1000+ apart, but most people dont have enough land to be able to use the 1000 yard figure as a starting point! As long as its safe then I dont think it would matter too much how far apart you put them! The farther the better in my opinion though!

Here are some pictures of my most productive spot!
The picture is taken from where I sit looking down into a valley where a feeder is located! If you look close you will see my feeder with 3 nice bucks in it!
For this set up I dont even have a stand because I am up on a cliff looking down. The feeder is about 200 yards!

These are the type of set ups I look for when choosing a stand location! This is one of the most remote locations on this lease and you have to walk about 3/4 of a mile through the ceders just to get to it.