Vent loses are expensive, and some stations are venting from the vaporizers. Is this necessary for pressure release?

Gaseous hydrogen can be stored forever as long as the system integrity is maintained. However, liquid hydrogen is “use it or lose it” and will boil from system heat leak and build pressure unless it is used or vented. This is not usually an issue for continuous use or low-pressure applications which can use hydrogen gas pressure directly from the tank.  

For intermittent or high-pressure applications such as vehicle fueling, this can be more challenging.  If a gas compressor is used and if demand is regular enough, often the compressor can recover the boil-off gas. This is more difficult for a pump, but again, if usage is sufficient, then the liquid being removed from the tank can minimize or eliminate the need to vent.