The phrase "wearing thin" generally means that an object or situation has become less effective or less enjoyable over time. Antonyms for this phrase might include "gaining strength," "improving," or "strengthening." For example, if a relationship was wearing thin, it might be getting stronger as the couple worked through their issues. Similarly, if a person's patience was wearing thin, it might be expanding as they developed greater coping strategies. Other antonyms for "wearing thin" could include "firming up," "solidifying," "holding steady," or "maintaining momentum." Each of these phrases implies that something is getting better or more stable, rather than deteriorating.