Good question. Generally, people use service items to record services they sell to stay organized (i.e. keep items categorized accurately).
What's the thought behind switching them to non-inventory items? The data forms for each are nearly identical, so there isn't any additional data you could pull by switching andservice and non-inventory items both show up on the Products and Services list. I wouldn't want you to have to recreate your list unnecessarily if there isn't a clear advantage.
We wrote a quick guide for adding items to lists that might be helpful, check it out and let us know your thoughts behind organizing services as items.