What is everyone taking once treatment ends?

You'll want to look into DIM, Brevail (flax extract), and iodine since you're ER/PR+.

Waiting, I researched this question, too. Here is my opinion. Your list looks good to me, except for two items: I prefer food to the vitamin supplement, because of the idea that food gives you the right amount and combination of things without possibly overdosing and risking unintended consequences. And my oncologist, a post-menopausal lady, says the latest research indicates that at least for post-menopausal women, calcium supplements may cause more heart problems without actually preventing broken bones. She does recommend the vitamin D3 and low-dose aspirin, and is in favor of melatonin as a sleep aid. I get my probiotics from low-fat organic yogurt and kefir. I don't know much about magnesium. Congrats on finishing chemo!

juicing vegetables would give great absorbable calcium I'd expect

I had a follow-up yesterday at Vanderbilt's Breast center-mammo (looked good-first once since finishing treatment), breast exam w surgeon's PA (seeing the actual surgeon may take an act of God at this point). Anyway, we discussed my supplements at length and she stressed the importance of taking vitamin D and magnesium (they apparently worked together) and exercise (3 + hours per week) as effective ways to lower my incidence of recurrence. The first reg health care professional to really address this specifically.

My former onc did say eat healthy, cut back on sugar and processed foods and get plenty of exercise-but that seemed mainly to stem from her ideas of a generally healthy diet and lifestyle, not really to address recurrence of BC. She offered my tamoxifen for that (thanks, but no thanks).

Labelle, my onc is also into exercise to lower recurrence risk, ditto for D. That is the first time I hear "official" endorsement of magnesium though. Thanks for passing it on.