Five flats in a week?
Check your rim tape, possible flaws on your tires, and your installation technique. Do you always mount tires in the same position? Do you inspect the area around the flat every time?
Slits in tubes often means poor technique (you are pinching the tubes).
I use the cheapest tubes I can get ($2 each), and don't have problems with them, unless I install them poorly, or have rim tape issues.