From my experience (which, admittedly, is only about four years, I'm only eighteen), a slight arch in the wrist is fine, as long as it isn't too exaggerated.
When I had right hand problems (I still do from time to time), it wasn't my hand or wrist because I'm playing with a slight arch that feels comfortable. But for some reason, my hand felt cold and very weak for a while. Then, it was brought to my attention that when I rest my right arm on the edge of the guitar, I was pushing [way] too hard and this cut off the circulation to my hand, resulting in a cold, weak right hand. Now, I practice with a cloth or towel on the side of the guitar to cushion my forearm, and it seems to help. This goes to show the overall interconnectedness of the body. If your whole arm isn't relaxed, then tension is likely to move down your arm to your hands. Hopefully, when I go to study the guitar in college this September, I can get even more opinions on my technique.
P.S If anyone has had this problem and can give tips on ways to reduce tension, I'd be more than happy and ever thankful to hear it.