Mike,
If you have completed all 3 steps on the Standard Worksheet and ready to implement, I would implement when you know:
1. No one is in the NAV posting transactions
2. All possible Inventory related postings have been completed leaving the most accurate Inventory QOH, which will be effected on the Revaluation Journal. No pending Sales Shipments/Purchase Receipts/Consumption Journals/Output Journals/Warehouse and Inventory related transactions
Sometime the above is hard to pinpoint. Anything unposted, the QOH is what is revalued. After you run the Implement, the Revaluation Journal will be created awaiting your review and to Post.
Hope this helps.
Thanks,
Steve