The velvet "lips" on the suction tube obviously will get contaminated with particles on the LP that stick to them, rather than being sucked up with the cleaner solvent. This dirt can, in theory, then be spread around on the surface of the LP, which is not a good thing. (In reality, I usually see only a little surface gunk on the velvet, which is easily removed between cleanings by brushing or by scraping with a finger nail. I really think 95% of the bad stuff goes up the tube with the solvent.) To ameliorate this issue, I bought a few extra tubes from VPI. I keep one or two of them immersed in cleaner or deionized, distilled water, when they are out of use, so as to soak out any accumulated dirt. During a cleaning session, I swap tubes in and out every few LPs. You may want to have an extra tube around, in any case, in case the velvet pads come unglued; this has happened to me at least once.