Thanks for the question.
The answers to your questions are really situational depending upon how satisfied you are with your yard.
With respect to aeration, every year might be a bit too much. If your turf continues to be acceptable, aeration every other year or even every three years should be fine. Remember that the purpose of aeration is to improve retention of water in the upper inches of the sod and to promote good turf growth. If you leave your grass clippings on your yard after mowing and/or mulching your downed leaves onto the yard, the need for aeration is reduced as these organic materials will achieve these same objectives.
As for over seeding, this again is situational. In the spring before the turf has established itself after its winter nap, it is easy to quickly think of over seeding when many bare spots exist. Many of these will fill in during the early spring. The objective of over seeding is to establish turf in areas in which grass roots are absent. Grass spreads most rapidly during the latter part of summer – August to early September. If at such time bare spots exist in your lawn, then over seeding would be a prudent choice. If your lawn looks acceptable at this time, over seeding is not really necessary.
The following site contains an excellent calendar was to when various lawn tasks should be done: