The Royal Hours are like the monastic daily hours except with some differences in the psalter readings, there is a Gospel reading and the nature of the hymns.
The hours do not really last long, about 20-25 minutes each. So, stand for what you can and when you can't sit.
The standing part was not meant entirely in earnest. I can stand for more than eight hours, I am a relatively healthy adult after all.
More of my concern is that I have to prep myself for longer exposure to the incense. I have a at times severe allergic reaction to it.
Thank you for the info.