question: how long did it take your resident cat to cool off after getting a new kitten?

so i had a 1.5 year old resident cat and i adopted a 6 month old kitten and i feel very confident they’re going to get along. resident cat has her safe room and kitten has graduated to supervised exploring with and without the resident cat. they coexist peacefully if the resident cat has settle down for the night, but if shes up, she chases the kittwn under the couch. she used to hiss and now she doesnr, so progress, but how long did it take for your resident cat to let a kitten just exist?