He sleeps on futons piled up in multiple layers.
I apologize over and over again.
幾重 means many overlapping layers without specifying a number, whereas 八重 is conventionally tied to the number eight even when used loosely.
repeatedly; over and over again · in many layers; layer upon layer; row upon row
Compound of 幾 (iku, 'how many') and 重 (e, 'layer'). The exact historical derivation is uncertain, but the combination naturally yields the meaning 'many layers'.