They need to be precisely a 37.5° angle and aligned with magnetic north so they don't generate a dynamic static charge. You need to know the magnetic declination for the area where you travel to avoid magnetic capacitance induction of the bottle which will make it difficult to remove the lid. Avoid 67.2 MPH, as that speed harmonizes with the Earth's magnetic flux and the bottle may swell. Take care not to get colder than -90.8°C or the Nitrous will go hard in the bottle.
If you lay them flat or stand them up, try to avoid letting them get over 98° F if you can. If that happens it won't do any harm unless it blows a rupture disc, which isn't likely to happen. I haven’t ever seen a big bottle blow a rupture disc, I suppose because they are filled by someone who doesn't overfill.