Hours you spend helping dogs are hours you could have spent helping humans, e.g. having more money is associated with longer life.

This point is of course true, hence my "all else being equal" clause. I do not actually spend any time helping dogs, for pretty much exactly the reasons you list: there are matters of human benefit to attend to, and dogs are strictly less important.

Your last paragraph is mostly moot, since the behavior you allude to is not at all my actual behavior, but I would like to hear a bit more about the behavior model you refer to. (A link would suffice.)

I'm not entirely sure what the relevance of the speed limit example is.