You are being a good short-term team member, but that might not be the best for you or the team in the long-term. If you/other senior devs are getting the same random questions, maybe create a faq/run book? I've usually made it a point to say: here's the answer, now can you add it to the FAQ? That way, ideally, I never have to answer it again/that's the first place people check.
But in my mind there is a difference between being available for questions/advice vs. actually working, e.g. designing a system or writing code. If someone messages me on a Saturday asking, "hey, which server do I log into to do X?" then taking the two minutes to reply means I'm available, but I don't think of it as "work".