  Album length does not matter as long as it feels right. There are many classic albums that are only a half-hour long. An album's optimal number of tracks is ten; nine or less is an embarrassment and anymore than ten begins to feel drawn out and like padding, even if every song is gold.
Track number seven should always be the best song on the album. Never put your hit single first unless the rest of your album can back it up. Don't divide an album's tracks by musical style. Remember: if you do any time traveling, don't make contact with your future/past self; nothing good ever comes of it. 
