For what should be strictly a public service position and not something you seek long term profits or favors for, no person elected to ANY public office should be able to make a career out of politics for their own personal gain.
Set a lifetime amount in years of no more than 8 that any one person can hold political office in. Whether it be a CIA director, secretary of the treasury, senator or any other office conducting official business for the United States Gov't.
These positions should also be subject to yearly reviews, all the way up to presidency and if you are found wanting, you should be removed immediately. I am subject to yearly reviews in all my jobs. Why do you think you should be treated differently? You're not special