For example, assume a buffer is 16,384 samples. Also, assume a desired sample rate of 100,000 samples per second. The data window is thus 0.16384 seconds. This is equivalent to one period of a 6.10 Hz sine function.
Some new systems have real-time data streaming to hard disk.
Essentially, these systems can take data continuously until the hard drive is filled to maximum capicity. For these systems, the sample rate is the only practical constraint. Low-frequency shock measurement is challenging for additional reasons. Piezoelectric accelerometers and their accompanying power supplies are often inaccurate below, say 5 Hz. This is based on my experience.