Stop the wobble
A steel frame that creaks is almost never failing. It is loose. The distinction matters because one costs a warranty claim and the other costs ten minutes.
Bolted joints on any metal furniture bed in as they are used: the first weeks of climbing, sitting and turning over settle every joint by a fraction, and the sum of fractions is play. Play is what you hear.
The schedule
Retighten every bolt at one month, then every six months, in the same order the manual assembled them. Snug is the target; past snug you are stretching the bolt, not stiffening the frame. On lofts and bunks give the ladder bolts and guardrail bolts their own pass, because those joints take the liveliest loads.
If tightening does not silence it
Check the frame is square and the floor is not the culprit: a frame with one foot on a rug edge rocks on the diagonal and no bolt will fix geometry. Then check the slats clips. If a specific joint stays noisy with everything square and tight, that is the moment to contact the seller through your order rather than improvise with washers.
Placing a loft or bunk in a corner, with walls on two sides, braces the frame and removes two of the four fall directions. The paediatric source on our safety page recommends exactly this, and it is the single cheapest stability upgrade available.