it is always better to be prepared with an infinite number of yaks and titans incase the great calamity happens and they somehow permanently break, planning for the future!!!!!\
~edit
-thought rowley was good at pvm, but it might just be me being bad-
I mean I always bought a lot of summoning familiars in case I'd need them too, but ended up with something like 700 excess arctic bears, 300 granite lobsters and yak pouches were more often used to skilling than combat :l