Technical pens how long do they last?

I have some old technical pens I think more the 20 years old. The kind that you refill and take apart when you need to clean them.
I was wondering if any one knows if its time to throw them in the trash?
They are Staedtler Mars Matic ink pens. They came in 3 classic standard sizes in a plastic case.
I did know how to clean them nicely but haven't used them in a while. So when I did go to use them it made a mess. So I cleaned them again and it didn't improve anything.  I was wondering if the plastic distorts after awhile?
So what do you think?
Thank you for your answer.  :)

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ggom206 days ago

Got some Rotring made 30 years old unused, they look new.

Did clean some dried ones with ultrasonic cleaner cold water and

asoft alkaline based cleaner .

Na2CO3 diluted.

Regards

Kiteman8 days ago

My youngest "inherited" some technical pens that must have been over 20 years old.

A thorough clean, and they were fine.

They don't like not being used.
Plastic dries out, becomes brittle or simply looses some of its properties.
Some of these pens also use a tiny sponge inside to limit the ink flow - either at the top end or near the tip connection.
If you have one then it is a vital part of the design.
I had a bit of luck with my old models by placing them into hot water for a while, fully dismatled of course.
This can bring back the plastic back to shape and the temp flexibility allows to assemble it with better sealing then before.
If the ink leaks or drops out then it is usually a problem with air getting in somewhere.

Treasure Tabby (author)  Downunder35m17 days ago

Interesting. Thanks I'll try that. :)

You can also use some alcohol (not the drinking kind though) to soak the tip of the pen for a few hours.
This will disslove any baked on ink that otherwise might block vital channels.
Sometimes these little grooves on the underside are actually connected to the ink reservoir in some sort of a backflow valve.
As you use more ink for your drawings than what might run down these channels transport the ink back into the reservoir through the "vacuum" caused by the missing ink.
Hard to explain properly but you will see what I mean if it affects you.