Personally I can't be arsed with the whole sleepover thing but some of my friends are obsessed with continually having their DC's friends over for sleepovers. My DC are 8 and 6. My 8 year old has been to a couple of sleepovers at friends and we have had one of his friends back. He tends not to get invited that much - probably because I don't return the invite 
Am I impairing my DC's social development with my reluctance to join in the sleepover merry go round?