Localized estrogen (delivered directly to vaginal tissue most commonly via a ring, tablet, or cream) are very low dose and are not absorbed systemically. The prescription information supplied with these products has been the same as for systemic estrogen, which is taken orally. In November 2015, the FDA held a hearing on a change to the package insert for localized estrogen products to reflect actual research and clinical trials. While we still await FDA's decision on this request, we in the medical and research communities have not seen increased risk in localized estrogen use.
Some women who are concerned about estrogen use are breast cancer survivors. The American Congress of Obstetricians and Gynecologists (ACOG) recently published a statement on the safe use of localized estrogen for breast cancer patients. Safety for breast cancer survivors is a further reassurance to those of us who have not had that diagnosis.
All of this is to say, if the localized estrogen is the best solution for comfort, I think you can rest assured that it's safe to use for the next 30 years!