I keep suggesting this, but the solution is simple -- use the same system as the duty roulette daily bonus except apply to a weekly loot bonus.

Each day the first time you complete a roulette you get a daily bonus. You can keep doing the roulette for the rest of the day but only get the daily bonus once.

Apply this to coil.

Each week the first time you successfully complete a turn, you get a weekly bonus -- a chance at loot. Whether you win or lose the loot, doesn't matter, that is your weekly bonus used. After that, you can keep entering the turn for the rest of week but you only get the weekly bonus (the chance to roll on loot) once.