H.orientalis will breed without cooling or special triggers an at different times of the year depending of a variety of factors. While low pressures have been linked to success with some species and could have an impact in H.orientalis as well, they really are not difficult to get to breed at all. I always say that all they need is to be properly housed and cared for and they WILL breed. Mine always start breeding in late summer/early fall and their trigger would appear to be either a short period on land while they are moved from one city to another, or the drop of temperatures from 24-25ºC (not constant) to 20-21ºC. They are weird...
If you provide good care for them it´s a matter of time until they breed, no special cooling, light cycle or atmospheric pressure is required. Not that it can´t help, though...