Typically any coating is going to require some form of abrasive to remove them. To pinpoint that in years is going to be impossible.
Another thing people always forget with coatings is two things:
1.) Is this for a show-car or garage queen that is infrequently driven? >>>> If so, the coating will almost be certain to last for indeterminate amount of time.
2.) Is this a daily driver? >>>>> Longevity really doesn't come into play because my daily driver has been spot buffed so many times that 100% of the original coating no longer exists. As long as the car will take a daily assault of things that frequently need buffing/repairing, obviously you will re-apply a coating to that spot buffed area.
The longevity really comes into the horizontal panels (less apt to get hit with shopping carts, kids on bikes, etc...) and are more exposed to constant UV, thus less likely to get spot buffed and coatings re-applied. In that event, it's really not a question of how long the coating will last, it's a matter of when you will be doing your next annual sprucing (Clay, light polish, re-application).
3.) Yes, coatings offer a "candied" look.
As stated, there are many, many, many forum posts questioning longevity. The bottom line is, any and all coatings will require some form of "action" or "abrasives" to remove them. I'm sure on a molecular level they deteriorate over time (just as we humans do), but what that time span is, who knows....
Pro-Coatings with 5 to 10 year warranties require certified installers, which buy into radius protection (i.e. can install a particular product within an x-mile radius), and the company backs the coating against defects. With that you have to return to the said installer every x-times for their "sprucing" and they can be pricey.
Consumer products will offer near, like, same, kind of protection, and the question really is, where will your car be in 5-10 years anyway, which goes back to the items #1 & #2 above.
I would say, prep it yourself, do the coating. If you're going to keep the car for any length of time, get a full frontal of Expel or Suntek Ultra, and coat the rest of the car.