Due to the size and shape of these heads, we don't have a problem with "dirt" buildup on them. they press against the tape with enough pressure that they are kept clean. It IS possible for a tiny bit of contamination to "clog" the gap, in which case the head ceases to function, and you have nothing but snow on one or more speeds.
Now, enter the "CLEANING TAPE".
In the case of audio equipment, the heads are cleaned by WIPING the contamination
off of them. Someone decided that this was a valid method of cleaning video
heads, and the video cleaning tape was born. Since Video heads are not flat,
this method is not always effective, and indeed often causes MORE PROBLEMS than
it cures. They often wipe contaminants from harmless places INTO the video
heads. They can SNAG those tiny heads with the fabric many of them are made of.
The cleaning solution can dilute and wash out critical lubricants that can't be
replaced. They even cause some mechanisms to JAM. In short, WE DO NOT ADVISE
USING A CLEANING TAPE AS PREVENTIVE MAINTENANCE in VCRs. As a matter of
fact, here is a quote from Sylvania's warranty that was provided with their VCRs:
YOUR WARRANTY DOES NOT COVER:
Last modified: March 31, 2007