I think it may depend on your individual circumstances and as others have said whether the possible benefits are worth the impact on your quality of life. I was diagnosed over 7 years ago and was told from the start that hormone blocking for me should be for 10 years. I started on Tamoxifen (2 years), switched to Femara after ovary removal (for 3 years, 3 months) and then changed back to Tamoxifen due to quality of life issues. I have always found my oncologist good to discuss options with. They have the benefit of understanding the research but also knowing you as an individual with unique circumstances.