It's a bit of varied info for followup.
I had a mastectomy and DIEP reconstruction 6 years ago and had 5 years of Tamoxifen with annual checkups with surgeon and mammogram and ultrasound on opposite breast. Originally said 10 years Tamoxifen but ended up changing it to 5. Well 9 months after stopping it I have just had cancer reoccur in the skin of the reconstruction and have had to have another mastectomy. A bit devastated it has returned as didn't think it could after all that.
Make sure you get followups with skin ultrasounds as there can still be breast tissue cells left under the skin.
Not wanting to scare anyone but nothing is 100% and early caught is always better.