EXP boosting items only work upto 30, or specifically the Brand New Ring does. I don't know about the Ala Mhigo Earrings.

Preferred status expires after 90 days. After that, you have your rested EXP as per normal (additional % varying on the content you're doing) until that's used up. Then you're back to getting the bogstandard EXP values. So it could be a combination of all 3 expiring.