Audacity lets you record for as long and as often as you need, subject to the disk space you have available.
The disk space needed for recording depends on the quality (sample rate and bit depth/sample format) at which you record.
When recording, the audio data is written to your hard disk. For example, if you just press the red Record button without having yet saved a Project, it is written to Audacity's temporary folder. Therefore, the amount of time you can record for is limited by the available disk space on the drive you are writing to. Audacity lets you know the amount of time you can record for based on that remaining space, giving a clear indication in the Status Bar at the bottom of the screen as to how much time you can record for:
The time remaining depends on the current space on the drive, and on the quality (sample rate and sample format/bit depth) at which you are recording.
If you record to Audacity's temporary folder and then save the recording as an Audacity Project this will take longer as the project file has to be copied from the temporary folder to the proper folder.
Thus it may be preferable if you are intending to save a Project to save an empty Project before you start recording, with the
That way, the recorded data will be directly saved to a permanent location/folder in your file structure.
When the recording is over, and now and again during editing, use File > Save Project > Save Project (not File > Save Project As ) to update the Project.
To get more recording time:
Note that reducing the sample rate will reduce the audio frequency limit. 44,100 Hz gives a theoretical maximum of less than 22,050 Hz that can be captured. A sample rate of 22,050 Hz gives you less than 11,025 Hz. For speech, you can take out the high frequencies without much loss of intelligibility. Likewise, reducing the bit depth reduces the dynamic range of the audio. For example, 16-bit gives a whopping 96dB of dynamic range. 8-bit recording reduces dynamic range to 48dB. A 22,050 Hz, 8-bit recording would rival the sound of a good quality cassette tape.
Note that disk space usage above relates solely to the size of audio data held by Audacity, not to the size of audio files exported from it. You need this space to record and edit, but if you do not save an Audacity Project, the temporary data is deleted and the space released as soon as you exit Audacity.
When making a longer recording of a few hours or more, other computer resource issues may be involved apart from disk space. These include the need to have sufficient RAM and swap file space available, and ensuring automated events such as system or application updates or screen savers are not able to disrupt a recording. Having stable, up-to-date sound device drivers properly matched to your hardware also becomes more important.
Audacity stores samples as 64-bit values (even on 32-bit machines); therefore there is no inherent 32-bit limitation that recordings may not exceed 2^31 samples in length (which is for example just over 13.5 hours at 44,100 Hz sample rate).
44,100 Hz now offers a theoretical maximum recording length of a mere 58 billion hours or more than 6.6 years (if you have the disk space).