Future Segment in New COA

Summary

Field Length for Future Segment - Can it be changed after implementing?

Content

When creating a new COA for my client we are including a Future segment.  I have been under the impression that the length of the segment value cannot be changed once the COA is deployed.  Is that in fact true?  

I was reading the document attached to this 2017 post, "Cloud ERP Guided Path and Configuration Best Practices".  On the Best Configuration Practices Tab, under General Ledger, Future Segments is this Best Practice:

Because it is impossible to predict the future, and because it’s difficult to change your COA structure post-implementation, it’s a good idea to consider implementing one or two additional segments for future use.