The phrase "are often fluid and" is correct and usable in written English.
It can be used to describe situations, concepts, or conditions that are changeable or adaptable in nature.
Example: "The boundaries between different genres of music are often fluid and can lead to innovative collaborations."
Alternatives: "are frequently adaptable and" or "tend to be flexible and".
Dynamics were often fluid and expansive, though where the score called for sudden, sharp contrasts, the players usually magnified the gulf between forte and piano.
Conversely, as with any breaking news story, information is often fluid and the authoritative media updated the story with the official explanation as soon as it was provided.
How they impact on an individual's decision-making is often fluid and may change in a person's life and career cycle.
Similarly, synthesising data from various published qualitative studies, Germeni and Schulz 30 concluded that the boundaries between seeking and avoiding information throughout the journey of patient with cancer are often fluid; therefore, information seeking and avoidance should not be necessarily viewed as two distinct behaviours pertaining to different groups of patients.
The overall demand for PPEs and related supplies is influenced by country plans – and these are often fluid.
At the United Nations, however, situations are often fluid until the last minute, as envoys work the telephones to their capitals, and governments confer over the heads of their diplomats.
Studies indicate that such diagnoses are often fluid, changing as the child grows older, though severe behavior problems often persist.
13 Contrary to north Bali, the organization of irrigation in the south varied by locality while boundaries between village and subak were often fluid.
Importantly, the experience in this study and from other research with sex workers in Madagascar is that the distinction between main partners/boyfriend, called "sipas" in Malagasy, and clients is often fluid[ 16].
