How long does each IV drip session last?

How long a drip runs matters for planning your day. It also sets how long you need to watch for a reaction while the line is in.
Drip length depends on the bag
There is no fixed time that fits every drip. Ask whoever prepares yours how long it will run, how long you should stay once it ends, and which signs matter once you leave.
Watching the clock and your body
Stay for the full time you were given after the drip ends. When the line goes in, ask which changes during the drip you should report to staff right away, and save the number to call once you are home. If something feels like an emergency, call emergency services.
How long one research infusion ran
If you want one example from research, read the pilot study of the human plasma and urine NAD+ metabolome during a 6 hour intravenous infusion of NAD+. It describes one long infusion in a research setting, not a typical drip time. If tolerability is the worry, read the small study of how patients tolerated IV NAD+ compared with nicotinamide riboside, which is about how people tolerated the infusion rather than timing.
If you want the wider science, read the PMC review NAD+ biology and supplementation: from mechanisms to clinical perspectives. If you want a plainer summary, read the Cleveland Clinic article on NAD+ supplements, benefits and risks. None of these sets a time for your drip, so the person treating you still has to give you one.
Planning a drip around your day in Long Island City
When you call to schedule, ask for the total time from arrival to leaving and whether you can go straight back to work or home. Afterward, note what you feel and when it began.
A time from the clinic beats a time from the internet
A drip time you find online does not replace the one the clinic gives you for its own mix.