How long should I take Arimidex?

[margarita46]

I had breast cancer in 2008. It was the second time around  on the same bbreast! The doctors told me that it wasn't a metastasis, but a second primary.
The first time it was in 1998, and I had a lumpectomy, radiation, and took Tamoxifen for five years.
The second time, although the cancer was quite small, since I couldn't have radiation on the same breast, I had a mastectomy, and reconstruction.
I have been been taking Arimidex, since the summer of 2008.
I saw my oncologist today for my yearly check up, and she told me that I could stop taking it.  I am quite anxious about stopping: after taking Tamoxifen for five years, at the suggestion of my then oncologist, I stopped. I am still wondering,
If I would have had the second cancer.
So, here I am again: what do I do?  Is it safe to continue? Is it helpful to continue?
Your opinion will be greatly appreciated!
Thanks!