3 hours is about normal. The infusion itself only takes about an hour, but the setting up, testing urine samples, getting the IV line in, doing all the drugs paperwork etc can easily take an hour before you get started, and then aftterwards they like to keep you there for an hour or so to check for no bad reaction. So I would say planning on 3 hours is about right. In my experience, people who are working go to their jobs afterwards as normal, but it would be sensible to let work know that delays can happen, so they shouldn’t expect to see you bang on 2.00 or whatatever.
Seating space in these day-case rooms can, indeed, be limited, so if you want to take someone with you they might have to just sit in the cafe or something if there isn’t room for them.
Apart from being time-consuming, the Tysabri infusion process isall pretty straightforward and untraumatic. TBH I’m better with someone else sticking needles in me than I am with sticking them in myself (long-time Avonex user before Tysabri.)
I hope it goes well for you.