First, let's assume that you are asking about the USAF(this is an international site).
You normally cannot stay at a base for an entire career. I have known a few enlisted people that have stayed at a base for most of their career, all of them CONUS bases, and many of them crappy locations. Even they had to work something with the assignment system to go to Korea for a year before they could come back to that base. I knew ONE guy that managed to stay at a base for 20 years--he spent most of his career as an E-5 and barely make E-6 in enough time to make it to retirement. You have a higher chance of limited moves if your job has limited bases (say Minuteman maintenance).
Overseas tours in the USAF are only about 2-4 years (depends on the location and whether or not you have dependents with you). After that tour, you can APPLY to do another back to back tour there. Assuming that it is approved, you wouldn't be able to do a third.
Germany is a highly sought after assignment, and you would be lucky to even get it. You could end up in a job that doesn't even have the option of going there. Some career fields are cracking down on people staying overseas forever because that means that some other schmuck is stuck in North Dakota.