For these goals I think you could just repeat SSB I & II, Sustained Power Build, [repeat]. No need to do Century Speciality unless you have a specific event to prepare for. Otherwise you’re just trying to get your FTP as high as possible while optimizing your weight.
Use Plan Builder, choose the “I don’t have any events” option, and pick something like the Gran Fondo emphasis (or any other that interests you and aligns with your goals) and you should be set.
In addition to his advice, sometimes I just create an event even though I don’t race to help me time things. Example - I’m going on a 10 day vacation. I’ll make that my event so that I peak right before it and then have an FTP test the week I return and start my next phase.