If you run out of stamina in above 120 feet come to a complete stop and dismount, while in midair it will not lose stamina if no one is on it. Therefore that also means you can chill on one and watch a Gigs swallow Rexes.
To know how much time need to the next feeding just do the next. Look the Food number# then that number multiply x 10, then divide /3600 and the result will be the number of hours until the next time need to be fed. F.E the food number is 1850.5 1859.5x10=18595 /3600 = 5.1 hours
A fire wyvern is one of the best you can have because they are resistant to fire damage so alpha wyverns are much easier to kill same with all the wyverns they can't hurt each if they are the same element but the bite attack still works on all wyverns keep this in mind