almost at the end of the visibility (at least in Europe) here a conclusion of He6678 observations mainly of members of the ARAS group (and some others).
The V/R measurements of ten cycles led to a period of 550 (+/-) 2 days. Compare the result published in Be Star Newsletter: 40-2012 with 541 (+/-) 15 days of 5 cycles.
Any comments are welcome!
It is interesting to point out thaty delta Sco is a "star of many periods", or maybe only timescales. Apart from the 10yr binarity and the 550d V/R, there are as we'll shorter photometric cycles. They began with about 60 day time scale, and lengthened to about 100 days, see adsabs.harvard.edu/abs/2013AJ....145..142J