With respect to operating days, I think the key point is demand. If demand is high enough, then Orbite will be running the HPA facility 24/7 regardless of statutory holidays and will adjust shifts / schedules / personnel as required. The premium on employee salaries to cover shift work bonuses and the mandatory overtime built into certain schedules that involve 24/7 operation will be more than compensated by the money made on extra production of the plant. As others have pointed out already, 24/7 operation regardless of holidays is not uncommon.
Although it is very process specific, in general startups and shutdowns (particularly startups) are tough and can lead to high costs and challenges from a product quality standpoint. It is usually easier to leave equipment running ... it is actually harder on a lot of equipment to have it frequently started and stopped as opposed to ran continuously. Ovens or calciners, for instance, like to be operated continuously as opposed to subject to frequent heating/cooling cycles which can affect refractories, seals and metal components. Even if Orbite doesn't get contracts for full theoretical capacity, they may still opt to run 24/7 regardless of holidays and then choose to do one major shutdown a year, say in summer, particularly if the process generates a lot of heat and hence makes it harder on people and equipment during hot weather.
Maintenance requirements will also dictate schedule. From my understanding, Orbite wants to scale up by using duplication of lines and this lends itself well to continuous operation. You can shut down one line to do maintenance while keeping the others going and thus you minimize the impact on production rate. If required (likely), you then do a full shutdown once a year to do major work that can't be done on the fly, as others have already discussed here.
Long story short, as long as there is demand for the product, I think there is a very good chance that Orbite will be running the HPA plant around 340 days a year or more.
Good discussion and points by many on the board today in this regard and lots of plausible scenarios. Thanks again in particular to Alumina1 for your great post.
Good luck fellow ORT shareholders!