Do tarantulas get used to being handled?

i have 8 t's (a redknee, 2 rosies, fireleg, antilles pink toe, costa rican zebra, oklahoma brown, chaco GK......sorry, names are not the scientific ones) and all of them except the pink toe let me handle them whenever i want. i can also cup all of them and flip them on their backs and rub their bellies,lol. does anybody think they get used to being handled, cuz mine sure as hell dont seem to care when i pick them up :)