Hi all :)
Just a quick review on these pens :)
I have used them daily for at least 5 years - DWC/NFT
I have NEVER cleaned them or used caps.
I have NEVER changed the batteries.
I have checked them for calibration a few times - not once have they been off.
Cost me around £60 IIRC when I bought them, honestly I cannot fault them. I have had expensive ones, cheap ones and these are the best yet :)