Hi, the water is just fine 
Interesting questions, but nearly impossible to answer. I’ll give it a try, though.
Simple answer: It depends! A straight forward, already well known, well documented scale or score will take only a few weeks - given the resources to make the archetype, run the review and enough reviewers. Hirsutism scales Observation Archetype: Hirsutism scales [openEHR Clinical Knowledge Manager] were uploaded to the CKM Oct 5th and published Dec 22nd last year, and that turned out to be a not very simple score because there were variants in use. Karnofsky Performance Status, Observation Archetype: Karnofsky Performance Status (KPS) scale [openEHR Clinical Knowledge Manager], were made in January 2021, but stayed in Draft until May 13th 2022, when it was put on review. It is likely (as it seems from the review comments per now) that it can be published in only 4-5 weeks.
More complex concepts, as the family of Imaging exam archetypes, have taken years - not in continuous work, but on and off. The main thing is the resources with deep knowledge to build archetypes and who also has insight in similar archetypes in order to reuse their pattern, access to domain experts to define (clinical) content, insight in available terminologies, and of course community input during the review process.
Medical devices are infamously known for not being standardised. For example ventilator manufacturers seems to deliberately name their ventilator settings differently - causing hard times for clinicians who have to know the differences (or likenesses) between ventilators from manufacturer X and Y.
So again, it depends on how complex the device is, and if there are any universally accepted nomenclature or terminology for the settings/readings.
A way out is to make generalised archetypes, with common name of elements representing settings or readings - if they exist, and map whatever dataflow from the device to these general nodes. And preferrably link them to a terminology either in the archetype or at template level or run time. Examples: SNOMED CT, Loinc, DICOM, etc.
There has been attempts for making archetypes for “breathing” - including disposable devices, as tubes, and ventilator readings. Again, on and off. I think “off” is the status for the work right now. It might be restarted if and when there is a concrete usecase and a customer/vendor willing to spend hours in taking them further.
Surely there has been done work locally, and quite certainly taken into production as local/national or vendor-specific archetypes. Not what we strive for, but as a necessity due to time and/or resource limitations.
I’m not trying to disencourage you and your potential client to start making archetypes for the medical device in question - actually on the contrary, but you should know that there is a need to find the resources to help you out both in terms of investigate the content, do the archetyping and the standardisation process.
To the others in the openEHR communituy: Please fill in, and shoot me down if I’m wrong!
Kind regards,
Vebjørn (in the Norwegian archetype team).