The bottom line is you have to keep an eye on him. There are very few domestic horses that can go barefoot with neglect and get away with it. Just because he doesn't have shoes does not mean he doesn't need to see the farrier every six or eight weeks for a trim. As a matter of fact, regular farrier care is one of the principle keys to success. Your farrier will keep little chips and cracks from becoming great rifts and chasms and will be able to spot potential problems before they become serious.
Proper trimming can dramatically increase the likelihood of success.
Trimming for shoeing and trimming for barefoot are not the same kettle of fish. It takes a highly skilled and knowledgeable farrier to keep most horses barefoot successfully. It is not just a matter of whacking off excess foot and rounding up the edges. Such questions are not easily answered correctly by an unskilled or inexperienced farrier and there are no shoes to protect your horse if your farrier is wrong. If you are looking to save some money by allowing your horse to go barefoot, you will be money ahead by hiring a top flight farrier who charges more because your horse will be able to go without shoes for a longer period of time.