I used to split my map services in the app as discussed, so just a warning that it totally throws off any service stats. If you have a service with 10 layers that are referenced individually each site hit results in 10 service hits, this happens whether the layer is set to visible or not - some stats can be adjusted but many can't.
I had to accept the loss in functionality as i need accurate performance stats, the performance loss wasn't bad at all though, i certainly never had any complaints from users.