Is there anything to do with the monster summoning thing if you like your monsters?

It's unclear to me what I am supposed to do when I find a summoning thing if I like all three of my monsters. Are you supposed to swap early monsters for later monsters despite the loss of exp or are the later summoning things just kinda useless? I figured there would be some way to decline the summon for an exp boost or something but I didnt see that option.