When it fits
When a feeder makes sense.
A feeder is the right structure when you want to aggregate a group of investors into one LP line in the master, ringfence a particular investor base, or open a strategy to investors who need their own vehicle. The operating model is identical to running the master, the feeder is an additional compartment, not a separate machine.
For investor bases that are sensitive to tax leakage in the master's domicile, a feeder can be paired with a Luxembourg corporate blocker.