I have killed a lot (24) elk from a tree stand. The last two years I hunted area I have never hunted before and got elk both times. Both area have a lot of water. In some areas water is not going to be the magnet it is in drier locations, but there are elk trails and saddles where elk are funneled in when they travel. As cnelk said, don't set up a stand willy-nilly. Go where you can see there has been frequent and recurring use. Rubs, different ages feces, or tracks can aid you in determining frequency of use. Places where several trails come together at a water hole that is dirty is great.
You do not need multiple stand locations, if additional quality ones are just not there. Elk most likely won't be around every day and it is unlikely it will be the same ones, so they don't know when they come walking in. Sitting in a stand be careful about all movement when elk are present. A tree stand is no free pass to get away with anything and everything. You can remove obstructions for shooting lanes if necessary, but I like some vegetation around to break up my outline. You can make your own if it helps. Elk are not real intelligent when it comes to those things, but they have good eyes.