GEO3s going for FHQ posting still have a very long runway. They would be in their 3rd to 5th year of service at that point, and are likely slated to be promoted to GEO4 in their second and final year of their FHQ posting, at the latest. When they take up their first KP role after HQ, they'll be about 5 to 7 years in service, which seems quite 'normal' - except that they also already have one HQ posting under their belt

For "farmers" it is much, much better to go into HQ after serving one tour as a SH/LH/AYH. First of all, you would already be GEO4 or higher. Next, you get access to the full range of positions available at Enhanced Posting Support on your way out of HQ.