I've also been on Advair for years now (250). And until about a year ago, I took it in the morning and at night. I actually found myself forgetting to take my morning dose a lot of the time, and I was getting by fine. So I just cut that one out all together, and now I take just the night time dose. I've recently tried to cut down my dose again (once every 2 days), but it doesn't work for me--by the time the second day rolls around, I can definitely tell a difference in my breathing. This is very dissapointing because I've had problems with Oral Lichen Planus (similar in appearance to thrush) since beginning the meds years ago, and recently it's been quite bad. So I'm going to try something different I think. But not for a couple months because I'm currently pregnant. After the baby's born, I think I'm going to ask about Symbicort.
Good luck with your weaning!