Nrmal mra 8 years ago. 2 of my 2nd degree paternl relatives had fatal brain aneurysms age 38 42. My doc says no repeat mra needed. What should I do?

Difficult question. I think you should be screened - see: http://www.Ncbi.Nlm.Nih.Gov/pubmed/10648430 and: http://www.Ncbi.Nlm.Nih.Gov/pubmed/14752379 the fact that your relatives are 2nd degree relatives is reassuring. The fact is: no one knows the best screening frequency for this. I wish you well.
Discuss. It doesn't sound like your previous study showed anything. If you are that concerned, discuss that with your doctor. If a repeat study is negative, try to relax.
I think worthwhile. I think given your family history, it may be reasonable to obtain a 3t tof mra (no radiation, no contrast so very safe) every five years. Particularly around the perimenopausal time is when it might be worthwhile. The average age of aneurysm rupture is 52. Please see brain aneurysm center for women for more information.