To be fair to Numatic, I think they've hit upon exactly the right formula for Henry. From a user's perspective, outwardly it's still the same cleaner they are already used to, that functions and performs exactly as they would expect. Any changes over the years have been incremental, to keep the cleaner up to date and address users' wants/needs, but without going so far as to render it unrecognisable from the original.
It worked for the Hoover Junior, Lux Twin Turbo, Kirby and Oreck, to name just a few examples. Lots of revisions "under the hood" with a few styling changes thrown in along the way, yet still essentially the same product when all is said and done. Familiar enough to keep repeat customers happy and coming back for more, but still with something new to offer for those considering the product for the first time.