Hi all, I agree with Jimmy White to a certain extent, better not to train at all than to train in bad weather.
With regard to distance, you have to ask, why are you training them, I would say that for club racing you need not go far at all, in fact a lot of sprint flyers do not train after the first race.
If you are flying in the national for instance, the birds need to be fit, but they also need to have the confidence to break and go their own way and not follow the drag, so more distance and single up will help them.
Just my opinion
All the best Mick