The phrase "most on-and-off" can be replaced with a variety of synonyms depending on the context. If it relates to consistency, words such as intermittent, sporadic, or irregular could be used. If referring to a relationship, fickle, wavering, or capricious could be appropriate. In terms of work ethic, lazy or unmotivated fit the bill. Similarly, if discussing a person's attendance, absent or flaky could replace "most on-and-off." Overall, it is important to choose the correct synonym to convey the intended meaning accurately.