FYI, a good chunk of metal-on-metal or metal-on-plastic glue failure is user error.
-Did you wash the mini? There are lubricants on the pewter which aid in taking pieces out of the mould, and this lube is still on the mini if you use it straight out of the blister/box.
-Are you using the right kind of superglue? There is better stuff out there than the GW crap. GW glue is made for plastic and metal, which means it's not very good at either, just adequate. A proper metal-to-metal superglue works wonders.
-What condition are the joints in? Too little metal-to-metal contact and it won't work. But if you have two perfectly smooth flat surfaces, it ALSO won't work well. Ideally, you want good contact, then rough it up a bit with fine-grit sandpaper to give the glue pores to fill into.
-Did you pin the joint? As others have mentioned, pinning is a key to larger minis. Some, like Carnifex or Hive Tyrants, actually NEED to be pinned, simply because no glue will hold their weight.
-Touch the glue... The thing super glue bonds best with is human skin. If you are holding together two pieces which just won't bond, tap-touch the joint a couple times. If it can peel just the dead layer of skin off your fingertips, then you press the pieces together and rub them a bit (like an arm, put it in the socket then move it around a bit), your skin will accelerate the bonding and make it hold more firmly.
Just some handy tips from someone who's assembled well over $10K worth of 40K.