Although I can't find it now, I read a study about aggregates in 7 different pharma rHGH formulations.
The GH that came with sterile water, not BAC, so were single dose / immediate use vials had the least aggregation and lowest rate of reported side effects.
Aggregates take time to form, an "incubation" period. The more time, the bigger they get. The larger they are, the more likely they are to cause immune reactions. That's not to say sides were definitely the result of aggregates, perhaps the lack of anti-aggregation ingredients in the immediate use formula HGH was the reason, but there's a lot of circumstantial evidence pointing to aggregates being responsible.
This applies to all peptides, by the way. The longer the chain, the more susceptible they are,
My preference is smaller dose vials of whatever peptide I'm using, so they spend the least amount of time reconstituted.
If it's a peptide used intermittently, like PT-141, hanging around for a long time, I'll filter the dose just before administration to reduce the number of large aggregates. A small reduction in potency from degradation is no big deal, but I'd rather keep the aggregates out to the extent practical.