My almost 8 week old takes super super short naps. Like 10-20 mins. I recall LO1 taking at least 30 min naps, but LO2 will wake up 10-20 mins after I've put her down. All day, every day. After the 10-20 mins, I go in and rock her again. I did this with LO1 also, but I can't remember whether the naps lengthened naturally, or whether it was after nap training.

Do they lengthen on their own, and when?