I'm not sure why it's worrying me now as he's always been a big sleeper but is it an issue/red flag of any sort for an older baby or toddler to sleep too much? My boy is 20 months and sleeps 13-14hours overnight and around a 2-2 1/2 hour nap, so he's really only awake 8 hours a day. He's a big lad (99th centile), developmentally no concerns, and energetic when he is awake. I think he may have poor vision though, not sure if that could have an impact or if there could be anything else to check. I did wonder about his thyroid as I have hypothyroidism but they check that at birth and he was fine.