I do agree with Painted Horse and themacpack and others comments on using wraps or protective boots on the trails. It would be ideal to not have to use them at all.
However, with that being said, I will share my 2 cents on the subject. I have worked with many horses who have worn protective boots for turnout either half day or full day turnout for as long as up to 8 or so hours and have not seen any problems from it. My own horses have worn them as well for turnout, especially in the winter when they are shod on all fours with winter shoes as precaution against interfering/brushing, sometimes they don't get as much exercise as they should in the winter and they don't always get turned out for as long as usual depending on the weather, so when they are turned out they play hard! Winter shoes can leave your horse with a nasty injury if they happen to knock themselves while playing around. They have worn them in deep snow and even some mud without any problems, and my horses are all thin skinned, sensitive thoroughbreds. I have also used them for trail rides lasting around 3 hours. I also know a lot of fox hunters who wear them while out hunting without any problems. All of the boots that I am talking about here have been Woof Wear Brushing Boots, either the all purpose Club boot, the Single Lock boot, or the double Lock boot. I have never seen these boots cause any problems for any of the horses who have worn them for turnout and/or riding.
If you choose to use boots on your horse, there are some things that you can do to help to minimize the risk of boot rubs and irritation. Make sure that the boots you choose are the right size for your horse and fit well. Learn to put them on properly with right amount of tension, not too tight, not to loose. Keep your horse's legs and boots really clean. Brush your horse's legs well before putting on the boots and make sure the boots are clean, you can even give the inside of the boots a brush off. After riding, if your horse's legs get really sweaty it is a good idea to hose the legs off or sponge off to clean off the sweat, also a good idea to hose down the boots and let them air dry in the sun if they are really sweaty but not too much dirt on them and then brush them off when dry. If only mildly sweaty and not dirty just let them air dry and then brush off. If they get really dirty, and also on a regular basis, like once a week or so even if they don't look too dirty, it is a good idea to wash them with mild laundry detergent, add a second rinse cycle and air dry the boots. Also remember to keep your horse's legs really clean, regular brushing, especially before putting on the boots and hosing off if they get really sweaty and once in a while washing them thoroughly with mild shampoo or even a medicated shampoo.
Also, brushing boots only offer protection from brushing or any knocks and bumps, they are not supportive boots, they do nothing to support the joints, tendons and ligiments in your horse's legs. I don't have any experience with using support boots like some people have mentioned the proffesional's choice or other styles similar to those, so I don't know if they would cause rubbing or if they would be ok to wear for longer periods of time.
If you choose to use boots, I would recommend the Woof Wear brushing boots. Woof Wear - Protection By Design - Woof Wear