if we're talking canines, most males (applies to humans too) will do anything to not have to work for their orgasm and will get "lazy" or even expect you to just suck them off. orgasm without any "work" from them is all pros and no cons.
do keep in mind that this doesn't apply to every single dog, at least not at first. letting the part of your body that bites anywhere near their most sensitive organ is a pretty hard line to cross for some. they will get "lazy" as the rest eventually too if there's enough trust to let you cross it.