A conversation that comes up frequently involves the next edition of IEEE 1584. This standard is still going through the long revision process but here is the question that comes up.

When a new edition of IEEE 1584 comes out (likely to be at least another 1.5 to 2 years), arc flash software will be updated to reflect new changes.

The question is about REVISING EXISTING STUDIES for your / your client's facilities.

How long after arc flash software is updated with IEEE 1584 would you begin to REVISE EXISTING arc flash studies and labels?

Facility Owners - ASAP for our facility(s) <1 Year
Consultants - ASAP for clients < 1 Year
Facility Owners - 1 to 3 Years
Consultants - 1 to 3 Years
Everyone - When the NFPA 70E 5 year review period is reached
It Depends - Something Else

Based on the hints that have been dropped assuming that the final revised calculations are not extremely compute-intensive such as Mike Lang's time-domain based model, the actual programming time is likely to be minimal and there is going to be an awful lot of attention to the subject so likely the "1.5-2 year" software window will be more like under 6 months.

Answer though for the end users is that it depends on what comes out. Examples:
1. Model results require substantial updates to the field surveys--this entails substantial cost so there is a big push to not redo it until the 5 year cycle hits. But if the changes are effectively just to update software, the update should be pretty rapid.
2. Model results substantially change the incident energies reported upwards. Proactive organizations will want to push for an update quickly.. Others may actually intentionally drag their heels for as long as politically possible.
3. Model results substantially change the incident energies reported downwards. Probably lots of interest in using the new model as soon as practical.

What will be interesting is what comes out of the "2 second rule" subcommittee and the "don't bother modelling" (<125 kVA) subcommittee. Hopefully somewhere along the way someone will establish a threshold for when an arc flash is possible so we can move on.

I think realistically, for consultants at least, it will be "when the client issues a P.O."
For those that view arc flash as regulatory burden with no real value, that will be the 5 year mark,
plus however long they think they can let it slide after that.

For those that see real value in arc flash protection, I would say it would be within 18 months of a revised standard coming out.
With that time being driven by budgeting cycles.