re: Does a toilet go bad?

Over long enough time frames the glaze on the porcelain can get degraded by cleaners and then start accumulating scale inside. This can make the toilet performance a little worse. The bigger issue is that if your toilets were cheap ones that came with your house, if they are the older low flow models, or if they have 2 buttons then they suck. Spend a couple hundred on a new one with upgraded larger bore internals (American Standard cadet 3 is an inexpensive option) and the difference is huge in how fast and strong it flushes.