I have to keep fit, I have to keep 'tied to reality', I remain practical, and have to socialize with many people, all day... sometimes working (for example) in a small hut with the same 10 people for 6 months... in a desert. All in all, it challenges me in many of my weakspots, and prevents me from over-using my strong points (computers!). So, as far as 'the challenge' goes, and for self-development purposes, it is still a very good job for me!
Anyway... been here three years; and at present I plan on staying here for another 10... or maybe another 20. There is little reason to change; no other job can offer the diversity and scope of this one!
Oh, and as a result of working late four days this week, most of us have today off. We deserve it!