OK buckie you'll know this, as an owner of some older machines. Is there a delta where an older kettle seals perfectly but an OLD one no longer will?
Case in point, yesterday's cook, using my dad's two machines. His '05, after being shut down, was stone-cold (out door "room" temp) in an hour or less. You couldn't tell, inside nor out, that just a little earlier it was 450 degrees in there.
His '75 18.5" daisy wheel, shut down same time, was too hot to touch still ... and cleaning the top grate produced sizzle and smoke as stuff hit charcoals ... none of the bottom wheels seal worth a damn anymore. It's as if years of tugging on them to open/shut involved some downward tugging away from the kettle, bending them. I don't know how to bend them back sufficiently and don't necessarily want to replace them?
My '92 seems somewhere in between. The One Touch sweepers are new and tight but I don't know if it's ever cooled down as fast as my dad's '05. All of the lid vents on these seal OK and so do the lids as far as I can tell. Nothing "too clean" about them, that's for sure.