I would think full timing has little impact on credit rating. As long as you don't do anything to damage your credit rating it should stay good, however if you are no longer working or have income when you go to borrow money you may get a second look even though your credit rating is good. I kinda experienced this recently when I purchased a new truck. My good credit rating allowed me to get the lowest interest rate but if I was not at a bank who has known me for a long time the "measley" retirement check (i'm not old enough for social security yet) may make some lenders balk.