Who's doing the "work" on replacing your 2 rear main seals and mostly, does he know that sealant needs to be applied to the flex plate to crank bolts? If no sealant was used, that could be your repeat problem now.
Otherwise, was the oil leak correctly diagnosed, like is it really a rear main and not perhaps a cam seal above that that's leaking and the "tech" then sees oil in the rear, lower part of the engine and assumes it's a rear main?
One needs to degrease, add dye if necessary and then drive the car, carefully examine the source(s) as a rear main seal doesn't just go bad twice unless the installer botched it (and yes, also possible).