right now im taking cave keys as reward. i have 3 characters with everything lv4 ( for the cave items) and one character with everything level 4 except combo all lv3 plus have some lv 5's but only 2 or 3.

the best choice for now is to keep on getting cave keys till i have the runes lv 5 or higher? and than take coupons? or cave keys is always the best choice even if you have them lv 6 or more?