I had a tarantula more than ten years ago. I kept him in a 10 gallon aquarium with rodent bedding (He liked to burrow under it). I kept a moist sponge in there and he would bite and suck on it for water. He was a bit of a pig, I fed him six crickets a day and he killed and ate all of them in under ten minutes. I thought he may be underfed but when I added more crickets he started letting them live for six-twelve hours at a time. I would let him crawl around on me sometimes, he was a beast to anyone else and tried to bite them. I don't know about special care because he never seemed to need any. He was small for a tarantula but healthy. He lived for several years with me until passing away in his sleep one random day.
It was probably old age, yes. He was already an adult when I got him and he lived a few years with me. Where I live, we did use a heat lamp in the winter as needed. I think he would bite others because he could tell they were tense and afraid. It made him tense and afraid. I was always comfortable handling him so he never bit me because he had no reason to be afraid. At least, that's my theory.
Oh, I'm not allowed to have a new one where I live or I would! I'm not sure because it was more than ten years ago but I'm fairly certain I kept him at just above room temperature (Around 75-80 degrees). He's suited to live in the desert so I was always worried about him being too cold. I don't think there's any way to tell a tarantula's age. As a rule of thumb, the bigger ones tend to be older but mine was a bit small than other tarantulas his entire life so it's not that accurate.