What is the life expectancy after repairing an aortic aneurysm?

It depends. It depends on your overall health. Typically if the aneurysm is larger than 5 cm the risk of rupture is fairly high about 3-15%. Greater than 6cm about 10-20%. If successfully repaired then your life expectancy returns to near normal. Decision to operate depends on the aortic size and the estimated risk of surgery.
Better. Before, you had aneurysm with all the risks that come with it. Now, after treatment, these risks come down to general population level. Life expectancy will depend on factors other than because of aneurysm that has been treated successfully. Enjoy life and its ongoing responsibilities and accountabilities.
Entirely unchanged . A major aneurysm trial showed that life expectancy does not change at all following a successful repair of an aortic aneurysm, whether it is done by the traditional open approach or minimally invasive stent graft. The only thing repair does is take aneurysm rupture off the list of possible things that can kill you (i.e., aneurysm-related mortality). Discuss further with a vascular surgeon.
AAA Risks. It depends on the age at which the aneurysm was repaired. I am not aware of any data to suggest that an uncomplicated repair, open or endovascular, results in a change in life expectancy. The risk of dying from a repair depends on many factors, but should be <1% for an endovascular repair and <5% for an open repair.