IMO this drill teaches the dog to run blinds with his nose to the ground. After all, he's been rewarded with a bumper every few yards. Running blinds with his nose to the ground is a very bad habit.
Much better to start at the end by identifying a pile of bumpers and work back from there. Start at 25 yards or so. Toss a bumper on the pile, send dog on name. Receive dog in front finish, cast to pile on "back" back up 10-20 yards to receive dog for next send. Repeat as you move back to desired distance. This way the dog has no expectation of finding bumpers along the route, is not affected by scent along the way, and has the expectation that bumpers are at the end of the field.
Either way you choose to proceed, recalling a dog crushes momentum. You are trying to establish or build momentum. Don't recall unless you get a really flagrant flare on the initial line. Like if dog pointed at 12:00 and dog's initial line is to 3:00, recall and move up and/or reidentify the pile or line.