Hi Crystal,
I'm so thankful to hear what you are doing for your mother and that you have found something to help her - Bless the Lord!
If you can alternate the oils/blends without losing efficacy, then that seems like a good plan to me, but I have read/heard that because the oils are variable from season-to-season (batch-to-batch), there is not the same concern that one would have with a pharmaceutical. I have used one blend daily now for nine years (Vitality for thyroid support), and I don't feel like it's lost any efficacy for me.
I hope someone with actual experience like you describe will offer their experiences. From what I've read/understood, people are using the same oil/blend daily with no loss of efficacy. The hope would be, if it is possible, to help the body come into a balance so that the support would no longer be needed. That may or may not be possible in these cases, but we can pray that the Lord will give wisdom for how to continue to help her with natural methods that don't cause more harm. May ALL your efforts be blessed!
Linda