You really don't have to worry about most orphans. We owned a 2007 Holiday Rambler Endeavor for 9 years which was an orphan when HR was acquired by Monaco and then Monaco went belly up.
All the components such as heating, air conditioning, refrigerator, and electrical are common through out nearly all brands orphaned or not. Most chassis, engine and transmission components are likewise used across many product lines. Cummins, Allison, etc. parts are readily available. Your biggest issue for an orphan might be replacement body parts.
