Just wondering if Libra's get too comfortable.....

Do libras get so comfortable around someone that they back off with the flirting, and the passion seems to die?

Seems to be, on occasion, yes. The usual astrological response is they need to go find their balance. Psychologically, it's described as having to recoup and sort yourself out. General dating description: if you've been 'won' the 'winner' either a) doesn't feel the need to continue the effort, b) feels you were won too easily, or even c) some other stuff has come up and it's bothersome and he/she just isn't feeling so well right now.

But with astrology in perspective and Libra being an air sign, if you feel the need to say something to him/her, logicize your feelings as best as you can and speak up. Make it simple and non-accusing (because it could indeed be subconscious), something like: "It was so nice when you would [example]. It made me feel like [this]. I miss that. Did you like it, too? Let's do [similar idea] together. It could be fun!