What was that breakup rule?

Re-watching s.a.t.c for the umpteenth time got me the answer to a question I had awhile back.

In satc:S2:Episode1 (yes there's a reason why this resembles biblical citations) Charlotte says,

"... it takes half the time you were in a relationship to get over its breakup."

E.g. If total duration of relationship = 10 years
Then the time it takes to recover from the breakup = 10 years/ 2
= 5 years
:
If this were true of marriages, by the time you're ready to re-marry, well let's just say you'd have miss the ball game.