Microsoft is providing Extended Support for Windows 7 (if SP1 is installed) up to January 14th 2020. This means that they will continue to provide patches for security threats and other hotfixes up to and including the cutoff date.
This is not particularly relevant for a pc that is not installed in a company network or domain. However, as we adopt a policy to steer customers towards having their pcs online for remote support (even if only very temporarily), security patching remains important.
The wider issue is one of hardware availability and common business and/or consumer pcs are not available to buy with Windows 7.
Fanless, solid state industrial pcs running Windows 7 Embedded are still available to buy and I have implemented a number of these in the field on behalf of our customers without problems.
Choosing an SSD, configuring the BIOS to boot on power and adding our programs (Datatemp DP) into a delayed startup routine allows a more or less "embedded auto-booting" system.
A PC with the following specification will cost in the region of 1000 EUR:
Intel Core i5-6300U 2.4 GHz CPU (4 logical core, 2 physical)
8GB DDR4 RAM
1 x RS-232/422/485, 1 x RS-232
2 x LAN, 4 x USB 3.0
2 x HDMI
1 x full-size PCI Express Mini Card slot (USB + PCI Express signal)
Size: 141.6mm (W) x 106mm (D) x 73mm (H)
Windows 7 Embedded (installed).
Search for (multiple vendors): eBOX560-500-FL.