How much flirt of the opposite party is allowed in a relationship?

Do you get accustomed to the flirt after watching your other party that okay, this is the level. "If she/he can go movie, I can go movie too" and likewise.

Or rather say, "why flirt in a relationship, why get married or get a boyfriend / girlfriend if you wanna flirt with other people"

People, when say flirting is fun, I may take up the level of flirting significantly with their significant others so avoid being impractical like "Hey, I am very cool woman/man, I can let you watch a movie but no kissing, and even if kissing then no smooching, okay?" because I know you are not that cool