[Captain_Lee]

Saltwater? From what I've read, it's a general rule to change raw water cooled risers/elbows every 5 years or so. When I changed mine, I wrote the year on them with a sharpie for my reference or any future owner.

You could use an infrared thermometer to check the temps of the risers/elbows. According to my surveyor, if they're much above 160 degrees, they're probably getting clogged with scale. Prior to changing mine, the highest temp I recorded was 185 while 135-145 seemed to be normal operating temps for the risers/elbows.

If it is in warm saltwater, for example, South Florida... locals typically change them out every 2 to 3 years.  It's pretty cheap insurance against the cost of not doing them!