personally… and take it for what you paid for it… I would not turn out in boots at all.
Getting small scuffs and scrapes is just par for the course for a young horse – unless there is a specific medical reason (like protecting a cut / keeping a wound free of dirt, etc) I would not be trying to cover his legs.
At best, it is asking for trouble. When I was a BM I didn’t have a “no boots for T/O” policy but we did have some boarders who really wanted their horses booted 24/7… The boots caused rubs from trapped dirt, abrasions, white hairs to regrow, bumps, trapped bacteria, got lost in the paddocks daily, one horse even managed to get himself caught in the fence with the boot… and in my frank observations (which are just that, so anecdote) the horses that were booted 24/7 were more likely to develop cellulitis or extreme inflammation to tiny little cuts, always had some sort of ugly bumping/white under the boots… etc.
And that’s not including the results having constant constriction on your legs does. The other drawback is heat, and dealing with it: there have been plenty of studies on cell death in overheated tendons and plenty of studies on boots during exercise: the academic consensus is that boots can cause the tendons to overheat, causing long-lasting cell damage or death in the tendon.
If you really have to boot to protect their legs, avoid the fleece lined boots. It gets wet and cold easily and traps a lot of sand/detritus. The thinner/less bulky for the job IMHO the better, as it is usually better at dissipating heat and less constrictive. Of all the T/O boots, I think WOOF boots are some of the better ones.