I think I've been in this hooby long enough to know how best my films should be stored. The only reason for mentioning this agin is because I saw a link to a so called professional film company .
The section on film storage did not specify 8,16 or 35mm film.
As far as I recall, some of the professional projectionists on the various forums always said the larger gauges, 16 and 35mm should always be laid flat horizontally due to their weight, vertically the film film would sag on the spools.
8mm films of 200,400,600 and 800 are fine to be stored vertically like books as the weight isnt there to cause a problem. My 1200ft 8mm films are also stores vertically and have been for the 22 years I've had my current home and so far, doesn't appear to have caused any problems.
Is there a right and wrong way for 8mm? Any thoughts?

In my humble experience the when I had to deal with 35mm the only reason the film would sag if stowed horizontally was because it had not been rewound poorly and not taped on the end.When you have a reel holding 6000 ft of film or bigger not a good idea to lay flat.
As to 16mm and 8mm each to his own.A lot depends on space mine are stowed flat /horizontally to fit the shelves and I do move them around,and they are all tight on their spools taped down.The problem is when a piece of tape slips and the film begins to loosen but if there's no problem with your collection leave well alone I say.

I store all of my films horizontally simply due to cans and boxes stay together better and won’t accidentally roll off the shelf.

I have heard the different views on what is right. When I see pics of archives it seems most are vertical, but they have well-designed shelves. I think archives like vertical storage as they can easily remove a print without having to shuffle things about if the prints were stacked horizontally.

I think Gwyn’s point of securely taping the ends is key for either vertical or horizontal storage.

I store both ways, if its in a box then it's vertical and in a can then it's horizontal, as long as everything fits then I'm not bothered how it's stored, I do tape the ends on all the films but only to stop them being damaged/squashed when the lids on,Mark

Mark, same my end, both, but 16s are horizontal only because i dont have proper archive shelves. 16s are no more than 10 in a pile though due to the obvious, weight.