I did not know that Ubiquiti was offering a standalone NVR now. That must be a fairly new addition. That was one of my big hang ups when I was researching their products about a year ago when I installed cameras on my house. I wonder what the maximum capacity of the Ubiquiti NVR is? My Reolink NVR caps at 6tb which gives me about 3 weeks of retention for my 4 cameras recording 24/7 @ 15fps (H265). I see their optional add-ons include 8, 16, and 24 TB drives so I assume it works at least up to that amount.
I might look into this further because I was considering going to something higher quality than Reolink in the near future.