Wear and tear on an FNC won't be bad, but parts can be a little difficult to find at times. For that kind of price point, I'd really suggest a lightning link for an AR15 - AR15 parts are much more available and less expensive, and the AR has numerous caliber conversions you can sill take advantage of, even in full auto.
As to the question some here raise of 'is it really worth it', I'd have to say for me the answer was 'yes'. I always wanted a machinegun and when I realized I could own one legally, I set out and did it. That was a few thousand dollars in transfer taxes ago and I still enjoy buying, owning, and shooting them. I may not take one out everytime I go shooting, but I always have a great time when I do, and I always have the option available to me.
Occasionally I do find I may get a little tired of one, but there's no rule that you can't sell it, trade it off later for something else you may like better, or add a little more cash and trade up. Heck, I've done it several times.