Was able to talk to their main sailmaker for a bit and he clued me into the age of the sails and gave me a touch of a tour. Pretty interesting setup. Saw that the main sewing machine is recessed into the working floor and the whole floor was the sewing table. The setup looked pretty interesting... the floor recess was done at the side of the building with the best light, so the machine operator usually has some good natural light to work with.
The sailmaker told me that I probably have original 30 year old sails as "we don't make 'em like that any more." My old sails apparently have a lot of hand sewn stress points and double eyes at the corners, which is an older practice.
He told me that neither tanbark or white sails have more longevity... that the materials are basically the same for the types of cruising sails I want. He also stated that mine are about 6 oz cloth, but that sail cloth weights have changed a bit over the 45 years he has been doing this.