Timeless is indeed difficult. You must know that all too well, seen your signature
Timeless is more on the bonus side as functionality is first and foremost. It is not so much an important goal as a choice to not aim for any currents trends or ornaments but rather aim for clean simple lines where possible. It might be a Scandinavian culture thing, but as a Scandinavian that is kind of the default mode.
Just do it, without overthinking about the thing being timeless, and everything should sort itself out eventually
Not really overthinking the timeless.
In my experiences though absolutely nothing sort itself out. Which is very sad indeed!
Everything has to be designed, simulated as needed, and tested. And every single little thing needs specifications for materials, sizes, tolerances and relations, surface quality, assembly, and making sure the parts are manufacture friendly. And preferably so across the various manufacture options which are economical optimal for various volumes of production..
Then there is planning necessary jigs for manufacture and assembly (and changing the parts as necessary), and planning for tests as needed to make sure that parts are indeed as specified. Add product packing and outer packing for shipment. The list goes on.
And the detailed level is necessary, especially for parts of the manufacture process that will be outsourced to others: Anything not specified will either be asked for, guessed or just randomly happening at the subcontractor. The result of that might not be pleasant - or fitting.
(I still have an entire pallet of some USD 30000 of cut but under-specified stainless steel somewhere around here from a project some 15 years ago.
And they say I don't learn?
Luckily it remelts nicely.)
Getting the design itself 80% finished is the small part of the work. The remaining 20% from say decently developed 3D design to actual product is by far the most work - and the most tedious and frustrating as progress is not very visible as such, and even the smallest of changes necessary in later stages tends to ripple through and make lots of extra work.
See, I'm a bit ranting frustrated here right now.
By user serviceable, I was mainly referring to materials: not some super steel that I'll need an angle grinder in order to restore a damaged tip or sharpen an edge. One of the things I really like about Victorinox MTs is precisely the use of permanent mechanickal fasteners -rivets
That is a good point. I thought of user serviceable mainly in terms of some disassembly for easier cleaning if needed, and possibly more disassembly for field repair, changing parts or modding. (And making sure it is repairable at all. Certain kinds of assembly will not undo nicely ever again).