Hiya.
My houserule...
Long Rests: "Houserule: After a long rest, a character can not take another long rest until he/she has been awake and active for a number of hours equal to their Constitution score. Extreme physical activity can reduce that in half".
So, a character with a 12 Con has to be up/awake for 12 hours of "normal activity" before they can get a good, solid, 'long rest' (re: sleep). If, as is likely the case for adventurers, they are in high-stress situations, fighting, casting spells, climbing cliffs, punching sharks in the nose as they tread water in raging seas, etc... then it would be 6 hours.
Yeah, this makes having a high Con a little bit of a detriment, but hey, who said life was fair?
And, as a bonus Houserule...
Fatigue & Exhaustion: "Houserule: A character will start to suffer from Fatigue (start to accumulate Exhaustion Levels), after a number of hours equal to his Constitution x2, of normal activity, or their Constitution x1, of high-activity."
This means that someone with a Con 14 can "stay awake" for 28 hours before suffering Exhaustion...unless he's adventuring or hiking in hills, mountains, badlands, etc. Then it's only 7 hours.
^_^
Paul L. Ming