It is its first bloom so I don't know how long the flowers last. However, if I refer to my T. megcalyptra, they could last 10 days or so.
There are 4 flowers on the spike. When I took the picture, the 2 lowest were fully opened, the one just above was opening, and the top one was closed. So sequential, but in the end all the flowers can be opened at the same time.
Thelymitras are a bit of a pain when it comes to opening their flowers: if the weather isn't sunny enough or it's not warm enough, the flowers stay closed. In addition, some species seem cleistogamous like T. vulgaris or T. luteocileum: their flowers have barely opened once but despite this they are producing fruit.