If you don't plan to swap for a airlock, then I'd clean them or swap for clean tube, stopper and bubbler bottle with new sanitizer or whatever you put in it.
Whether it's absolutely necessary, I don't know. But it'll look nicer for the next 10 or so days and your friends you show it too won't have that "ick" factor in their minds when they are about to sample your brews.
I leave mine on the blow off tube for the entire time now. If I was to be running shy on space where I keep my fermenters, I probably would use an airlock after the krausen is over.
Once the krausen has started to fall, I transition back to an airlock. Once that's done, I soak the tube in some PBW/Oxyclean/OneStep overnight. Then give it a rinse in hot water. If it comes clean, great, give it a shot of star san for the final step and hang to dry. If not, go buy ten feet from my LHBS at $0.50/foot and toss the dirty one.