Conditions. A condition lasts either until it is countered (the prone condition is countered by standing up, for example) or for a duration specified by the effect that imposed the condition.
If multiple effects impose the same condition on a character or creature, each instance of the condition has its own duration, but the condition’s effects don’t get worse. A character or creature either has a condition or doesn’t.
Exhaustion, however, involves levels of exhaustion; each instance of exhaustion will increase the current exhaustion level.