The stock swaybar bushings are a rubber compound. Aftermarket are generally polyurethane. I've had UUC and RD Sport sways on previous bimmers, and they always needed an annual relubing. I think some are getting better, with grease fittings, but they still need regular maintenance.
The end-links also made noise after a while. I had to replace one set of UUC end links after they got contaminants in the ball sleeve (I think it was sand) and nearly seized. I would service them annually as well.
Even with the maintenance, they are totally worth it, if you track or autox your car.