I had a S&S with my first 2 pregnancies.

DS 1 - I was 39 + 4 was also ripe and about 2 cm's had it done at 12pm and waters started leaking and minor labour pains about 4 pm that afternoon.

DS 2 - I was 39+6 had it done on my Dr's appt on the Monday, had a few stronger BH rest of Monday and Tuesday was a rip roarer of a electrical storm all Tuesday afternoon, sure enough woke up around 4am with contractions.

Good Luck, hope it works for you