A swiveling seat combined with John's straight-backed all arms method of paddling will probably buy you more time, Jay. As Richard states below, learn to read your body and you should be able to pull off a bunch more years of paddling without the ablation problems.

My thought here is that the arm paddling method will help you avoid the rotational issues with your spine. The swivelling seat will help your body turn to further reduce the spinal rotation. Any resistance to swivel that occurs at your butt is going to translate to your vertebrae, the seat should cause your back to swivel as a whole instead of twisting only parts of your back. Any swivelling should occur at your hip joints instead of around the L4-L5. If you learn to read the way your back feels when it's healthy then you will know when you are doing something harmful and you should be able to correct your technique. Of course, once your hip joints go you can always get new ones.

Robert N Pruden