Accepted answer
At 30 °C the question is which route is fastest, not whether aggregation happens — and the routes do not share an activation energy, so their ranking changes with temperature. 30 °C is 25 kelvin above the 5 °C middle of a 2–8 °C refrigerator. The ten-degree rule of thumb — degradation rate roughly doubling per 10 K — makes that about 5.7 times the refrigerated rate, which is an order-of-magnitude statement and not a shelf life. That multiplier is an average over every route at once, which is exactly why it cannot tell you which one wins. Molecules associate without any covalent change, so the mass is unchanged and a reversed-phase run — which is performed in organic solvent — mostly dissolves the evidence before it can be measured. So the way to answer it for your vial is to pick the method that sees aggregation specifically and run it against a control held cold, rather than to infer a mechanism from a purity number that averages all of them.
This is answerable from the chemistry rather than from anecdote, which is unusual and welcome.
Oxidation targets methionine, cysteine and tryptophan, adding sixteen daltons per oxygen. It is catalysed by trace metals and promoted by dissolved oxygen and by light.
Freeze-thaw cycling drives aggregation through concentration at the ice interface and pH shifts as buffer components crystallise out at different rates. Each cycle costs something.
Aggregation at air-liquid interfaces is established from surface-tension and particle-count studies and is the basis for anti-agitation handling guidance.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Swirl, never shake. Aggregation is a handling problem more than a time problem.