I voted 7-8 years even though I've only been in the hobby for about 6.
This is due to my purple, green & orange monti caps, which I've had since close to the start. I bought them as frags from a local reefer who I assume had them for at least a year before me, judging by the size of the mother colonies. They very well could be much older than I give them credit, but unless "Canadian Man" comes back to tell me how old they are, I'll never really know.