what this guy needs to understand is that language evolves; the correct usage is the one which people understand; 'until stocks last' and 'while stocks last' are no different in the meaning they convey to the ordinary person. Preserving language use for no other reason than to keep things the same is living in the past.
Diggerland is the worst, most boring 'theme park' in the history of theme parks. My son wanted to go as he likes diggers, (tut, 5 year olds!); you queue for 45 mins to sit on a digger for about 3 minutes to do some digging; it's just terrible.
I don't think the article is correct though, sometimes people get depressed about things that happened in the past for which there is no solution.