Welcome to my Humble Shop! I look forward to helping you!
I briefly touched on this on my Services Page so here is a little more detail. Traditional lacquer is called Urushi. It is extremely difficult to get outside of Japan so I use a standard clear polyurethane lacquer. The main benefits are that when done properly, helps hold the wrap even more firm without sacrificing grip quality. (Many practitioners say the feel its better with lacquer however that is all personal preference of course). Secondly is added protection against discoloration and moisture damage from heavy or repeated use.
It is never a bad time. All kidding aside, telltale signs of a tsuka in need will be you may notice the kashira is loose. Also, over time the ito may start to discolor and the folds can become loose.
I do not use synthetic cotton because it is a highly unpredictable material. It is extremely difficult to work with as almost all of it that I have found is not well made and makes for an unclean look when introduced to glue and tight folds.