If you're using barrier tubing you're already ahead of the game vs. ~70% of bars and restaurants. (Unless they have a glycol chilled long-draw system) So I'd say you're doing great! Unless you have a chilled beer line, you might want to flush it, simply due to the taste issue, otherwise you /should/ be okay.
For most at-home systems, if you're able to finish a keg in a few weeks then cleaning on E is fine, like Keith said, 4-6 weeks is appropriate. I was just stating the recommendations by the Brewers Association. You start getting intro trouble when you wait MONTHS before cleanings.