Just after the 10-hour mark, the order at the head of the field was shuffled once more by the third full-course yellow of the race, triggered by the #19 GEAR Racing Lamborghini Huracan GT3 Evo of Tatiana Calderon stopping on track with a fuel pump problem.
That benefitted the #77 Mazda RT24-P, as Tristan Nunez had just come in for a routine stop before the yellows flew, but the American driver negated that benefit by picking up a drive-through penalty for passing under caution.
With the #10 Wayne Taylor Racing Cadillac taking the chance to change its brakes during the FCY, the main beneficiary of Nunez's error was the JDC-Miller squad, with Duval pulling away over the course of the 11th hour of the race to establish the #5 Cadillac out front.
By the end of the following hour, the Audi DTM ace had pulled out a gap of 14 seconds over Ryan Briscoe in the WTR car, which had climbed from fourth to second after its brake change.
Filipe Albuquerque had the Action Express Racing Cadillac in third after taking over from Pipo Derani, just under 30s off the lead, but pitted just shy of the 12-hour mark, promoting the #77 Mazda with Olivier Pla at the wheel.
Pla took over from Nunez midway through the 12th hour and passed the #6 Acura Team Penske of Simon Pagenaud before moving ahead of the sister #55 Mazda of Ryan Hunter-Reay.
PR1/Mathiasen Motorsports pulled out a big lead in LMP2 ahead of its main rival DragonSpeed, after the latter team opted to put in Bronze-rated Henrik Hedman during the FCY.
Gabriel Aubry managed to pull out a lap on Hedman before handing off the #52 Oreca-Gibson to Nick Boulle, who was 1m20s ahead of Colin Braun in the DragonSpeed car.
BMW held a narrow advantage in GT Le Mans over the two Porsche 911 RSR-19s after 12 hours, after the #24 M8 GTE staved off a strong challenge from the Risi Competizione Ferrari.
James Calado had moved up to second after the FCY in the #62 car and was chasing BMW man John Edwards until he had to pit and make way for Davide Rigon, at which point both Porsches - who had got their driver changes out of the way prior - moved ahead.
Laurens Vanthoor was less than a second behind Edwards at the 12-hour mark at the wheel of the #912 Porsche, and 2s ahead of Nick Tandy in the #911 car.
The #3 Corvette C8.R ran fifth behind the solo Risi Ferrari, with its sister #4 car still stuck in the garage and looking unlikely to return to action.
A superb stint from Bryan Sellers at the wheel of the #48 Lamborghini Huracan GT3 Evo has put Paul Miller Racing in charge of the GT Daytona division, some 6s clear of the WRT Audi R8 LMS driven by Mirko Bortolotti.
Sellers had been sixth under the FCY but made short work of the cars in front at the restart to make his way through to the lead, while Bortolotti passed the erstwhile leading Pfaff Motorsports Porsche 911 GT3 R to grab second.
The Pfaff car dropped down the order when Zacharie Robichon pitted to hand over to Lars Kern, meaning third in GTD is now held by Toni Vilander in the Scuderia Corsa Ferrari 488 GT3, followed by Andy Lally in the GRT Magnus Lambo and Aaron Telitz in the best of the AIM Vasser Sullivan Lexus RC F GT3s.
The GEAR Lambo rejoined the action after its fuel pump problem, having lost 37 laps.