My kids are 18 and 14, and I've done my best to encourage creating things instead of consuming things.. but sometimes they need some down-time, and so do I.
It's going to be harder to keep these boundaries as your daughters grow older and their natural personalities develop. They'll likely take interest in whatever their friends and social peers are doing, and the two of them may go off in wildly different directions. Stay engaged and be ready to adjust your parenting techniques as the girls grow older.
But seriously, additional children come with their own pros and cons. Plus, of course, there's the thing about wanting more than one child.