By the time that the oil dries out, won’t it run poorly hinting a service without even having a timegrapher, and before the gears grinding into powder? Serious question here
You may not even notice that it's running poorly until it is too late. From Archer's post I linked earlier :
Timekeeping is not a reliable indicator that a watch is in need of service. I see watches often that keep great time, but are a mess inside as there are many components inside a watch that are not directly related to the timekeeping function. Certainly if your watch suddenly begins to lose or gain time, this can be a sign it needs service, but the absence of a change, which is what some use as an indicator of "everything's fine inside" is certainly not true.
By the time you notice something is off, it's usually too late to rectify the problem with a simple disassembly and some new oil. At that point repairs will be necessary.
As I said in my previous post, it's not the end of the world as long as it's easy to get the necessary parts. But when a manufacturer stops making those parts, or when you're dealing with in-house movements of companies that went under during the quartz crisis/revolution, it's a whole other story.
For example : If my 1950s Mercator (see spoiler) ever needs parts, I can either look for other Mercators on Ebay, buy all that seem to be a similar size and hope that at least one of them contains the correct part in a usable condition, or I could have the part custom-made by a watchmaker who specializes in these one-off cases. Both options will set me back several times more than the cost of a regular overhaul.