Petejack, changing the levers doesn't make any sense. Cables and housing wear out in the normal course of riding a bike; so does handlebar tape. Unless the levers start to rust, they'll last approximately forever.
You're going to have to replace the tape when you replace the housing. I'll usually replace cables and housing every 5,000-10,000 miles. It's nice to get some fresh tape about then, as well, and all three are down-in-the-noise cheap. Don't think the cables and housing need replacement? Don't want to take everything apart to check for fraying or cracking? Want to bet $20 against your life that the cables didn't fray in the last year when there's a stop sign at the bottom of a long, steep hill?
Go ahead. Replace the cables and housing. It'll almost certainly improve your braking. Then splurge for another $10-15 and put on new bar tape as a treat for a job well done.