I looked into this after we bought our boat. I know of lots of fresh water boats with rigging that is 30 years old.
I had ours inspected by a well known rigger in Florida. He suggested a few fittings be replaced because of possible corrosion. In the end I replaced it all. The rigging was 10 years old. The boat had been in saltwater for about 3 years.
If the mast comes down because of rigging failure it may not be covered by your insurance. Any rigger I talked to would not ok rigging more than 10 years old.
If you see broken strands then it is obvious the rigging should be replaced. A boat in salt water can have corrosion inside the swagged fitting and can crack without warning. I learned from riggers the recommended replacement interval depends a lot on the temperature and salt. The recommended replacement interval is longer in northern US states than in the Caribbean and shorter still in Hawaii.
The cost of replacement rigging can vary a lot. I had 3 quotes for new rigging. One from a rigger in Canada for $3k, one rigger in Florida for $5k. Then I went to a rigging manufacturer in Florida (Seco South in Largo), $1200. I went with Seco, really good work, rotary swagged, fast, honest.
Good luck, Bob