First Pregnancy (miscarried) this took us 3 years
2nd pregnancy (Olivia) 10 months
3rd Pregnancy (Charlie) 2months
4th Pregnancy (oooopsie, wasn't trying...was fully BF'ing Charlie and on the mini pill. Go figure!)

So for me, each time was quicker.

BUT, I have a gf in the opposite scenario.......her first baby was an oopsie, her 2nd took oonly 2 months, and she is desparately trying for a third, but it is taking its time......(16 months so far.)

So I honestly think it varies SO much between different women and varying circumstances (age, fitness, stress levels etc.)