Too Old for This...

As you accumulate more and more years, you feel the passage of time deep in your bones. For every three consecutive encounters without a rest (short or long), you gain one point of exhaustion.

FLAW. This is a flaw feat. At your DM's discretion, you may take this feat at level 1. If you do, you may also gain a feat, or increase two of ability scores by +1 (or one by +2).