Buy nuts, bolts, spacers, washers etc from a dealer and you’re paying for the whole 9 yards of warehousing, storage, summer holidays and then some.
In real life 40 Nm tips the scales at about 30 lb-ft. Interestingly enough that is about the same breakaway torque of cured Loctite 243 (the blue stuff) the difference being the Loctite 243 will not succumb to vibrations.
I’ll take a punt here that we’re talking about a steel bolt in a threaded aluminium casing. The problem is the steel can and more often than not will weld itself into the aluminium. Then when the bolt is withdrawn it pulls parts of the aluminium thread away resulting in the obvious weakness. We know we should be cleaning and examining the threads of all fasteners when taken apart but how many of us really do that?
All is never totally lost, bolts can be replaced and any damaged threads can be repaired with an insert. A careful inspection is required before re-assembly to avoid another bolt going AWOL.