There's really only one way to assemble these things;
There's two – badly, and well.
As for lasting 12 months – our wardrobes are rammed with stuff and have been going well for almost 3 years despite not having been glued and reinforced. So the finger is pointing at your skillz carlosg 😉
Btw we have tons of Ikea furniture and none of it's failed so far. Some of the chairs have become wobbly because they are held together with bolts, but this in turn means you can just tighten them up once a year, problem solved. Like it says in the instructions 🙂
Ikea – by far the best flat pack stuff I've done. And very very good for cheap furniture. When I was starting out I was determined not to go to Ikea because everyone else did. I scoured the city looking for nice furniture and found plenty but it was all £500 for a bookcase and £1.5k for a dining room suite. Anything else at Ikea prices was absolutely awful.
PS my wardrobes are staying put when we move. Too much trouble to take them down, and they probably won't fit a different place anyway.