The following Alchemist spells have bugged maximum duration - even if your caster level exceeds 20 (being in an arcane epic destiny), the duration is capped at CL20.

Greater Stoneskin
Goldskin Potion
Greater Evolution
Augment Armor

Other Alchemist spells, for example, Greater Liquid Courage, Feather Extract, Displacement Draught, properly have duration increased when CL exceeds 20. Please fix.