Good Riddles

Question: The doctor gives you three pills and tells you to take one every half hour. How long before you run out of pills?

Question: What goes in, down and out; but can't go in, up, out?

Question: I know all, have seen all, yet I am not conscious. Looking back upon me shows mistakes and also good things. Looking in the middle of me shows opportunities to be exploited. Looking forward upon me shows the effects of decision. What am I?

Question: What smells better than it tastes?

Question: Which is the missing number in the below Number Series? 2, 3, 5, 7, 11, 13, ?, 19