Jump, I think most people (self included) assume that when you ask a question like that it is relating to something you actually do. It certainly reads like that. Apologies if I misunderstood.
Tungsten is a very hard element indeed and filaments are strong and rigid when cold, but are close to their physical limits when hot. Shake a table lamp and watch the filament. When it is on it will swing around like wet spaghetti. Too much of that and it can snap. break open a bulb and handle the filament, it is stiff and hard - not going to break easily.
Interesting point about filament vertical vs. horizontal, but you'd need a detailed vibration analysis of that part of the structure to see if there was a big difference between the planes, and which most disturbed the filament. A big harmonic may well be the culprit, but finding it would probably be the research of years. Empitical advice from an engineer may well be the better bet.
There seems a great deal of practical sense in using reliable, effective automotive halogen units (or genny brushes), but your insurers will be thrilled at the get-out you provided in the event of a big claim.