The bad reputation that elegance corals have acquired in the past decade or so appears to be the result of a specific disease with an as yet unknown causative agent. Whether or not your elegance will survive long term depends very much on whether or not it's been exposed to the pathogen that causes 'Elegance Coral Syndrome' somewhere along it's chain of custody. There's a great article on it in reefkeeping magazine, which can be found here:
http://reefkeeping.com/issues/2008-01/eb/index.php
Unfortunately, elegances from the Indo-region are far more likely to have been exposed to this disease to begin with, and if it's been transported/housed in tanks holding other Indo-elegance corals at some point before you purchased it, it could very well have contracted it. You will know whether it's going to make it in a few weeks, a couple months at the most.
I can attest to the level of contagion of this disease - I had an Australian elegance for over a year, first as a very small specimen in a pico tank, then when it was larger, it lived in my 275. It was extremely healthy, inflating fully every day, and always exhibiting a healthy feeding response for just the time I had it. It tripled in size in the time I owned it. However, it wasn't as incredibly coloured as some of the fancier Indonesian elegances I kept seeing show up in stores, so one day I purchased another much nicer looking specimen from Wai's here in Calgary. At that point I knew nothing about Elegance Coral Syndrome (ECS). The new elegance began exhibiting symptoms of what I now know was ECS within a week of being in my tank, though at the time I thought it was a reaction to a new environment/lighting regime. The new elegance was completely dead 3 weeks later. I naively hoped that the new elegance would only partially die but still leave a mouth or two, so I left it in the tank until it was a bare skeleton. Shortly thereafter, my established elegance began to decline.
Here's some pics of the progression:
Brand new in the pico tank, scale is hard to gauge, but this was a 5 gallon tank, so you can imagine how small it was. This was January 16th, 2012
It was one of the first corals in my 275 and I bleached it a little right at the beginning because I didn't know how to program my lights properly - this was it nearly recovered on August 25th, 2012
This was it on December 28th, 2012. This is what this coral looked like every day, fully inflated, deeply coloured, always a great feeding response. It's 3 times larger here than in the first image. Unfortunately, this was also the day the last of the tissue of the new Indonesian elegance sloughed off.
Another pic from the same day (December 28th). You can see the skeleton of the new elegance in the bottom right
This photo is from January 6th, 9 days later. I thought the elegance was having a multi-day tantrum. I still didn't know what ECS was, or that this was the beginning of an inevitable end (it's the coral in the bottom right)
And finally, January 23rd, 2012
This was when I started doing some serious research in to elegance coral disease and realized what I had done. This coral followed the exact same progression as the Indonesian specimen, and started exhibiting symptoms 9 days after the new Indonesian specimen had completely died, after being vigorous and healthy for a year.
If your coral has been exposed, it's first symptoms will look a lot like the second last picture, it's tentacles will stay small and uninflated, and the oral disc will clamp, or generally not inflate. Then the tentacles will start to literally melt down to little nubs, and the oral disc will begin to take on a very unhealthy, swollen look. Finally, the oral disc will bleach completely, and eventually the tissue will begin to slough off. If this starts to happen, there's nothing you can do to stop it, and any other elegances you have in the tank are probably toast as well.
The good news is that if your coral has not been exposed to this disease and doesn't have it, it will likely be very robust and healthy for a very long time. You saw how quickly mine deteriorated once it had been exposed, so if yours makes it a month without declining I'd wager a good bet that it will be fine. If that's the case, I would never allow another elegance coral anywhere near the water that beauty is kept in unless it spent a couple of months in quarantine and was guaranteed to be clean.
Hope that helps.