These are 'free' services. Again, it's up to the owner (Esri) in this case as to if they will have any issues with a large number of hits. I would imagine that these already get a lot of hits, but if you are creating so many hits that they have to push out another cloud server (or 2, or 3?) then it might become more of an issue. If it was my server and that happened (and it was bogging my service down), I might just move the service often enough that you can't have an app consistently pointed to it. I would imagine that if it causes Esri too much money they would figure out how to stop your app from hitting their service(s). You can do it and ask for forgiveness later, or send them an email directly and decide if needs some form of payment over what is offered for free.
Maybe someone from Esri will answer this thread, but since it's mainly more from a technical side I would think not, or maybe they are passing it on to the sales/engineering group. If it was me I would ask forgiveness later, but you risk having it impact your app (if it's too many hits). Again, your call, but good luck.
