I think it really depends on each person.
My doc advised me to use oral not to have it at the moment in case I want to get pregnant later because it can take a while for your cycle to return to normal.
One of my friends was on it for 5years plus. She didn't have her booster because she hoped to get pregnant and never got her period because she got pregnant before it came. (about 3 months)
She unfortunatly lost the baby late in the last trimester, and it took ages to have a period again.
She fell pregnant about 1 year later but had only had 2 periods in that time. She is mystified as to why she hardly ever has periods yet she doesn't seem to have any problems getting pregnant
I think its really individual. THe trouble with contraception is we dont know our own cycle.
It takes my body the 1st month to adjust after being on oral contraceptives but the next month is my own personal cycle which is shorter.
After coming off the pill it took me 3-4 months to be pregnant with my son. I was 35 when I had him.THe other pregnancies have happened even quicker.
Good luck when the time is right