I don't think these ants are polygynous at all, so never.
Things to avoid:
- temperatures below 20°C (they are Asian ants that can't deal with cold and they do not hibernate)
- making the nest too moist (Camponotus in general like it less moist)
- disturbing them too much (especially during the founding stage)
- putting them into a formicarium too early (do NOT put them into a formicarium until they have at least 20-50 workers, before that keep them in a test tube of appropriate size, if needed put the test tube into an outworld)