assuming that it certainly depends on the type of driving and the type of roads, is it possible to make an assessment of how often to check if the carburetor is missing oil to understand the condition of the sealing o-ring or the correct functioning?

I filled first time on late 2023 out zenith stromberg, it was tuned/refreshed some years before.
true our car doesn't make a lot of mileage (less than 3000km meanwhile) but I want to define a "checking routine" to see if it needs attention on the next future or not and understand more about it :)

I'm not sure if you're still waiting for a reply, but as it's been over a month and no one has responded I'll throw in my two-bits. As my 122S with twin SUs got older, I used to check the oil in the damping cylinders at every oil change. It was rare it needed topping up, maybe every 3rd-4th oil change. I'm sure it could have gone much longer before being at the minimum level. If you're not familiar with it and as you likely go a long time between oil changes then maybe check it every six months until you learn to trust it and can go for an annual check as part of spring tune-up. Roughly every 2nd year I used to drain it and clean-it up before re-filling
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

thank you! the forum was down for a long time, so it didn't help much :)
from the post, I used the car only one time... but your experience is very useful. Surely my carburettor have needed more frequent topping than yours. I've made less than 2000km in last year and I topped it at time of this post. So I'll check it next months to see if it hace dried or not, or if an oil change could be a reasonable interval.
Thank you again!

My experience with SUs was over 50 years ago with carbs that were less than 10 years old at the time. Your carbs are over 45 years old so likely have a fair bit more wear and tear inside the damping cylinders even with new seals. Problem for me with something like this is if you don't make a habit of checking it at some kind of regular interval then you start forgetting to check it when you're busy. Good luck and hope you get to keep enjoying that old family car of yours for many years to come.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

thank you :D

this car was my dad's jewel, he bought it new and has only 108.000km on the odometer now. it has always been, and now it is even more, pampered and used with care: driving this car is for me anything but a matter of being in a hurry or being busy, on the contrary it is something for which the time spent driving it is only time well spent.

in fact my request is precisely to create a routine that keeps it in full efficiency and avoids causing damage to it :)

With that super low mileage and your loving care, just keep that car parked under cover so cancerous rust doesn't start in the rear storage wells, rear fenders, rockers and front floor pans then you can keep it going forever.
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Dave -still with 940's, prev 740/240/140/120 You'd think I'd have learned by now

Car has always and still is garaged, so it doesn't troubles me too much ;)