If your shaft seal looks like the ones on this site PYI Inc. | PSS Shaft Seal
, it is a PSS seal. The bellows is a maintenance item and should be replaced every 6 years if the regular seal, or every 10 years if it is the new improved version. This is manufacturer's recommendations. I am no expert on insurance (and the application of that type of law), but I would suggest that an insurer may not cover water damage caused by a failed, outdated seal???? Not something I would chance.
To replace this seal, the boat must be hauled, and the shaft disconnected and slid back allowing for removal and reinstallation. To my thinking, why not remove the shaft and change out the cutlass bearing as well, especially if it is the 10 year mark, as you would be almost there labour wise anyway?
These bellows provide the compression (springiness) to "make the seal", and over time lose this springiness as well as the fact that the rubber can deteriorate, especially if exposed to oils and fuels. If your leak is not the seal itself, then additional repairs to the stern tube will be required and removal of the seal would probably be necessary anyway for that.