Good questions!
Answer: it depends.
If you are a 17025 accredited lab you are to use the most current version of the standard unless using another version is approved by the customer. That would be good practice for a non-accredited lab as well, but not required.
On a practical basis, when you get a tool that was manufactured to meet the 2003 version of the spec it is most common to continue to calibrate it to that standard - the one that is what it was designed to meet.
However, if your customer has requirements that their tools comply with the 2017 version then you will need to calibrate them to the new revision.
Communication with the customer should clear these issues up.
