Existing behavior: According to the spell descriptions both contingency spells (SPWI617, SPWI908) have a duration of 1 day/level or until triggered. In reality, their durations are permanent until triggered. I have tried setting a duration in chain contingency, but the contingency opcode used (#234) is hardcoded to become opcode 232 (cast spell on condition) with a permanent timing mode.
How to reproduce the existing behavior: Cast any of the contingency spells and press Ctrl + T to try and force them to expire. Alternatively, you can open your saved games via SK or DLTCEP and check the list of effects on your PC. They are stored as opcode 232 (cast spell on condition) on the .cre in your savegame, and (incorrectly) with a timing mode of permanent.
How to reproduce the hardcoded behavior: Attached is a modified viersion of chain contingency, where the duration is set to 60 (one turn). Simply unzip the file to the override folder and test it ingame. The chain contingency lasts permanent until triggered.
Expected behavior: Even if they are not triggered, the contingency spells expire after 1 day/level.
Expected hardcoded behavior: Opcode 234 transforms into opcode 232 correctly with the duration values kept. Then it would be possible to edit the spell files to enable durations.
EDIT: Forgot attachment of SPWI908.spl