There are many low-priced hard disk recorders on the market.
The following products come with a monitor, and the internal hard disk can be replaced with a commercially available size.
Long-term recording is possible for up to 2 months.
It has four video (NTSC) input terminals.

 

 

Also, if you can use a PC without using such equipment, you can record long videos by using a USB camera or GigE camera and long-term recording software.