Using what may be considered today's "best" or "most secure" CSPRNGs, how much maximum data N can you read from a CSPRNG given seed input of length n before the output starts becoming predictable (without reseeding)? Can one read from it indefinitely and still get unpredictable output?
More concretely: can I generate 20kb of data from a hardware random number device, feed that to a stateful CSPRNG, get rid of the hardware random number generator, and indefinitely use the data from the CSPRNG for cryptographic purposes?
Note: I realize "length" may be problematic, so this question may be answered in terms of entropy quality.