Hi welcome to BW forums
Have you read any of the BW books? Tracy describes the 20 mins it takes LO to fall to sleep. I found it to be incredibly accurate when my DS was a new born and in the early months, each stage she described was exactly as he did, I could set a clock to the 20 mins it took too!
As mine got older he took less time to fall to sleep, he liked a quick WD and straight into bed then asleep. The 10-30 mins you describe sounds totally normal