For the first few weeks I was getting 1 per 2 challenges. Yesterday I got zero. I too paid a lot to get ships early on. My arena has 4 zeta's in the top 10. I can't beat any of them after being #1 for over a month. That fact is what bothers me. Meaning I feel the time crunch of being behind & wanting to catch up. Not sure how they got them so fast unless they buy blueprints & spend FS on zetas