This may be a stupid question, or it may just be up to personal preference, but should sheetrock be installed vertially or horizontally on walls? I've got 8' walls in a new office and I'm just wondering which installation would be better? Or if there's actually a specific code for wall installation.

I picked up three 5-gal buckets of premixed joint compound two years ago on sale, then my refurb project got put on hold. Never opened until yesterday, there is no bad smell to the compound. More like just a slight paint/putty smell. The mud is light greyish in color. I know mud has a shelf life, and I don't want to use stuff that really isn't good. I haven't yet tried mixing this up to check consistency, but if consistency is good, no smell, no mold, etc. is the mud really not usable being this old? I hate to throw money away, but I also don't want to spend time and effort using the stuff if it is somehow compromised. I have seen other forums talking about mold, smelly compound, etc. in partially used containers. That, I totally understand, would indicate that one wouldn't want to use the stuff. But I have only seen one suggestion that the holding power of the compound suffers with age. Is this true? Along the same lines, does even the powdered stuff go bad? I already used some setting compound, about the same age, to do my tape embedding. Seemed to be ok, but I'm new to this. Want to find out for sure before having to redo all my work! :-)