Are you doing what is best for you at this point in your life? And for your sister's family as well?

If so, you are absolutely doing the right thing. You are right where you need to be.

You don't have to justify, explain, or defend anything about your life to anyone so long as you're not breaking laws. I can see how your living arrangements make perfect sense. Beneficial financially and you're able to help your sister with the kids. What a boon! Move when you're ready and in the meantime, live it up. The kids will grow up too fast. I'd give a lot to live closer to my niece and nephew.

Seriously, are you happy where you live? Are you straining your sister's life, marriage, household? That's all you need to be at peace with.