There was a recent study by someone called Kaestle which I thought was interesting as it looks at the idea of sexuality through the lens of development— starting to move away from the fluid stuff but it still has some of that language. A lot people people try things out before figuring out what they like and what they don't like. If a young person puts themselves in the "sexuality is fluid" box I personally mentally put them into a "still working stuff out box". But my 2c, is that if you're an adult and still "fluid" then call a spade a spade and say you're bisexual. Ain't nothing wrong with that, but you give me the shits calling yourself a lesbian.