Cooler plug = engine longevity (?)
A dumb-sounding question, followed by my rationale for asking it.
1) how will a 'cooler' plug result in greater engine longevity?
The understanding I have with spark plugs is their heat range keeps them 'cool enough to avoid preignition' - i.e, not acting like a model engine's glow plug - 'while running warm enough to not accumulate combustion deposits'.
If a spark plug is too 'hot' for a given application, it acts like a glow-plug (due to glowing electrodes, no doubt) and it does not wait for the ignition coil to supply a spark. Instead, when the compression is high enough, combustion starts (preignition) which means a cooked engine in short order.
Is that what you meant by going to colder heat-ranges?
However, a 'too cool' plug not only looks like it's been working in the coal mine (covered with soot and caked with 'goo') but it tends to stop sparking. This causes an abrupt engine stoppage, possible bad language, and rummaging in the tool pouch for a spare (you did pack one, didn't you?) and the needed tools to replace the fouled plug.
Still, however, a 'colder' plug - one heat range from stock - may be wise. The original users didn't routinely 'peg' their throttles. Based on my reading of the lists here, that's not at all rare. Sustained wide-open throttle makes for a much hotter combustion chamber compared to the putt-putt-burrrrp-putt-putt of chinese traffic.
(As told me by an eyewitness.)
Second question: is the B6HS equivalent to 'chinese stock heat range', or is it 'a bit on the colder side' referenced to the Chinese plug(s)? Is a B7HS too cold?
