Duration of One with the Land seems to be a lot longer than hour/level. My other hour/level spells wear off long before it.
That is because it is turn/level, not hour/level.
I can see no mention of a change in the mechanic mods page, Skrillix. In vanilla NWNs OwtL is hour/level. Camouflage is the one that lasts forever, since it is 10turns/level.
Are you sure you are calculating your stats correctly? My one with land always wore off at approximately the same time as bull strength and barkskin whereas camouflage lasts a great deal of time.
Could you be mixing it up with trackless step?
I don't think so. I'm looking at my AE, which goes to 14 after casting and stays there for some time. I can double-check when I log in later tonight.
This spell was missed first time around. We'll rectify it ASAP (it is indeed lasting 27 minutes/level right now).