How long can my 6 month old go without eating at night?

Sa

My 6 month old had a bottle at 7 last night and we went to bed at 9. She normally wakes us up about 5 hours later hungry again, but last night I happened to wake up and it was 4:30AM (so 9 hours) and she was still sleeping peacefully. I went ahead and woke her up to feed her, but my question is should I have done that or just let her sleep?