Would you consider adjuvant endocrine therapy for DCIS in a patient who received bilateral nipple-sparing mastectomies?

No. This is chemoprophylaxis, and the very small amount of remnant breast tissue does not denote a risk of subsequent breast disease high enough to justify the toxicities and risks of endocrine therapy.

I agree in general. There are some circumstances where I would consider using tamoxifen; for example, someone with a higher-than-average risk of recurrence (i.e. those with BRCA gene mutations, very extensive DCIS, close margins, more than minimal residual breast tissue--which may be hard to determine). In those with osteoporosis, I might also consider it as a means of bone protection without the risk of estrogen.