Again, it's about organization. My scanner has about 150 FLs, likely around 1500 Systems (average about 10 Systems per FL - maybe higher). All those have Quick Keys and I can recall them fine because with a dozen or two exceptions, they are organized in a way that I don't need to remember anything more than where they are in relation to where I am. I likely only have 1000 Number Tags, but they are mostly for the primary PD/FD channels in my local systems, and then they share the same numbers as the FL and System Quick Keys with the CNT being 1 for the primary PD channel, and 2 for the primary FD channel.
Trust me - my memory isn't that great, but I can remember my Quick Keys and Number Tags since I organize them pretty consistently. For example, all my Departments are the same for ANY System in the scanner. My Systems use a map-based grid Quick Key, as do most of my FLs. Those FLs that don't are the only unique numbers, and there are maybe a dozen or two that don't use my standard format. All my 60s are for local things. The 50s are for PA and WV. My 40s are for Ohio (40 Regional, 41 MARCS, 43 NE OH, 45 Central OH, 46 East Central OH, Etc) - See how it is map-based? A 4 means Ohio. A 6 means the east-central part. From there, the Systems are county-based grids within the East-Central section. Department 1 is the PD for each System, 2 is FD, 3 is EMS, Etc.
When you have a plan, you don't need to remember what is where.