My T gave me his number and told me it was for business stuff, and not to text him about personal things, unless of course it was serious.

Our texts are usually regarding appointments or stuff like that. One time I text him at 8PM and freaked out after because I didn't realise it was that late, and thought he'd think it was inappropriate. He didn't mention it, but I've always made sure to text during 9-5, because I feel like when he's not working, he's exactly that; not working. I don't think it's right to text him when he's sitting with his family at night, I personally would feel weird doing that. But of course everyone is different.