I'm going to try and use the Keith brothers' _The Desert Environment_ rules which uses 'Endurance Loss Points' which you get for movement/heat/lack of water etc and then you subtract from the normal Endurance.  So far so good I can cope with that.

However, on page 10 it says "If at the end of any period of time, the character's total accumulation of ELPs *equals* that character's Endurance stat, that stat is reduced by 1."

The bit I'm struggling with is "at the end of any period of time".  Now, I maybe have my stupid head on, but it seems to me that it makes a difference whether you tot these up hourly or four-hourly or daily or whatever.  If I save them all to the end of the day, they can do (get away with?) much more than, say if I do them hourly.  So am I missing something?