I think you should use your own judgement according to the appearance of the foot.
We get few foot problems in our Hebs but the Shetlands with white hooves tend to be worse. We check everyone's feet at least once a year before tupping, plus at shearing, but there's not usually much to do. The odd hoof with a torn bit we feel should be neatened up before muck gets stuck up in the hoof and a problem begins. Feet with great long winkle picker toes do need to be trimmed in my opinion - why wouldn't you? Maybe in a very large flock there is the danger of rot bugs being passed from sheep to sheep on the foot shears or hoof knife, but with smaller numbers we can be careful about tool hygiene.
The ideal of course is to have some good rocky ground where they can play king of the castle and wear the hooves down. We have not a single rock, nor any hard standing they can use regularly, but plenty of wet grass which is hell on sheeps feet.
In the case of an actual foot rot occurrence, our first line of defence would be a dipping of the affected foot in Golden Hoof. Antibiotics would be the last resort and I am concerned that it appears to be the first line of treatment suggested.
We have an ancient Shetland ewe who we stopped breeding from years ago because she has a tendency to bad feet. I love her fleece though, so we keep her in the orchard with a couple of ancient Soays which have cast iron feet. The only sheep on the place which had maggots so far this year was this ewe - only in one foot. I suppose they were attracted to the smell
However, any rot had been well cleared by the maggots, with no damage to the flesh underneath - job done. Maggots used to be used in human wounds to clean up slough and infection - apparently it tickles a bit but is otherwise pain free. Maybe we should try it again with sheep
