Question: An air suspension fork on one of my bikes starts showing its age: noticeable play, scratches on stanchions etc. It has not become less smooth and does not leak air so far, however.

I am starting to wonder how safe it is to continue using it, and what will happen when it "fails".

Possible outcomes of a non-catastrophic suspension fork failure that I can imagine are:

1. All air leaks out and it compresses fully, becoming very short
2. All air leaks out and it expands fully, becoming at its full extension
3. Air air blows out, making stanchions loose in the legs
4. The fork just locks at random compression position.
5. Stanchions become so loose with so much play that it becomes noticeable at braking and steering.

What of these options are real, both for air forks and coil forks? Are there other failure scenarios resulting from a fork's old age but not a crash?

Answer: 
If compatibility is what you're after, you should know that it's not always necessary to use the same group. Many times, you can mix and match different groups, even different manufacturers.

As far as I know, all 10-speed Campy geartrain components should be compatible with each other. [You have to consider the capacity of both derailleurs](https://www.sheldonbrown.com/gloss_ca-g.html#capacity) relative to your gearing, but you have to do that even if using the same group for everything.
EDIT 2023: Compatibility was not a major issue when I originally wrote this answer but since then electronic shifting and some details in mechanical levers have changed things. See the [other answer](https://bicycles.stackexchange.com/a/87706/10595) and [this FAQ](https://www.velotech-cycling.ltd.uk/campagnolo_faq.shtml) for details.

---

No, the components are identified by name and year even if they aren't changed every year. Spare parts do have exact part numbers, and most of the small parts are shared between multiple groupsets and year models.

Compatibility is generally not a problem, all series after the old "pointy ergo" 9-speed from 90s have same freehub bodies and actuation ratios.