That's about the standard length of any survival horror game, so beating the game within 8 hours sounds completely normal to me. Re-playability is the key factor with this type of game and the unlockables (which I hear are a plenty), leader boards and co-op modes really help make this game very re-playable. Hopefully they will release some neat DLC for the game, I could easily see Capcom releasing an expansion to the game and giving their current track record it'll be well worth the purchase.