It's one of those horses for courses questions.
If your birds are alert and are exercising well around the loft. Then maybe this is OK.
But if they are not exercising well at home, then in my opinion they will soon become out of condition which will affect their overall fitness.
I believe training um throughout the racing season keeps that sharp edge on them.
They don't have to have extremely long hard tosses, but it keeps them working, its keeps them mentally alert and more than anything it stops them taking the piss.
Look at an athlete before the athletics season, they train long and hard, during the season do they sit around doing nothing in the period leading to the next race. Course not.
They fill themselves with a high carb diet and do one or two lighter daily training sessions, these stop them from stiffening up before a race.
It's just my opinion.