I've had this argument with many other instructors.
"Don't cancel until you have radar termination is sight"
"Don't cancel until you are cleared direct"
"Don't cancel until you are well clear of GTR (insert other airspace here)"
"Don't cancel until you are at least 3 miles to radar termination"
"Don't cancel until you are number one for radar termination"
I hear these taught to students on a regular basis, and they all make me cringe. First, they are techniques, not procedure, and if someone is downgraded for canceling early (yes, I've seen it more than once), that's a foul on the IP.
But more importantly, these are techniques whose purpose is to avoid, rather than promote airmanship. In every case they are meant to mitigate the possibility of making common VFR errors (getting lost, violating airspace, interfering with other traffic) by avoiding VFR flight all together. Not exactly building a strong skill set. And the result is a student (and one day a pilot) who only knows how to find a point by being vectored within 3 miles and then cancelling. Which, in my limited experience, often leads to misidentifying the point, due to only looking for a specific point (building, dam, tower, runway) instead of looking for the whole location (building between two freeways, dam on the north side of a oval lake, tower surrounded by chicken coops along side a river, runway with 12,000 feet of concrete and a military base attached to it).
Anyone with any exposure to UPT can see the AF aversion to VFR flight. I saw the same thing in the MC-12.
</FAIP soapbox>