The online booking system is only offering 15 minute segments in the mid afternoon, even for a full weekly pass. I presume that's just an aberration with the website and a weekly pass is valid whenever the area is open.
I'm not sure whether to book it, I've gone for exorbitantly priced one-off sessions on both Jewel and Anthem, and found both underwhelming to say the least. I have no interest in the heated chairs, and to be honest, I found the steam room somewhat weak and insipid on both. IMO, the free sauna and steam rooms in the dressing rooms on Vision class ships were vastly superior!
Is there a sauna in the Symphony thermal suite, and are the steam rooms actually hot?