I have two char sharing a bed. One has 58 agi; the other has 48. It seems as if the higher agi one recovers from similar length trips with less sleeping time. Is this intended behaviour?
Yes, it is intended behavior. Agility extends the distance you can travel before your travel weariness gets to max, so if they're both making similar trips the one with the higher agi will get less tired and thus require less sleep.