Hi ingdxdy,
The LPF is deterministic. After 62 cycles the filter blocks will output a new settled value. The HPF is more iterative and never really settles to a final value, much like an RC circuit charging. In fact, you can model the HPF as a first order RC-circuit with a time constant. Typically, an RC circuit will require approximately 17 time contants to settle to within a 24-bit level. For 31-bits, 22 time constants are required. Therefore, depending on what corner freqency you select, you can calculate a time constant (tau = 1/(2*pi*f) and multiply this by 22 to estimate the amount of time required for the HPF to settle. Typically the HPF will take much longer than the LPF to settle, so both filters should be settled after the HPF settles.
Best regards,
Chris