Lleva así tres horas
Ya no resisto más, lleva así tres horas - I can't take anymore, it's been like this for three hours. Is this right? Gracias.
Depends on what "lleva así" refers to. If it's a situation or an inanimate object, then yes, your translation is correct.
But if it refers to a person, say someone who has been unconscious for three hours, then:
"I can't take anymore, he/she's been like this for three hours"