The problems are technical limitations.
- Broadcom limits the max length of any undefined (i.e. added by me and not by Asus) nvram to a maximum length of 255 characters
- I already hack things a bit to extend that to roughly 1200 characters, but then you waste a lot of nvram while doing so, and that waste has to be multiplied by 5, for each VPN client
- On older models, you are already limited by having only 64 KB total of nvram - using 4000-5000 just for policy rules is problematic
- Each web page has a limit of around 64 KB of POST-able data, and the VPN client can eat a lot of that due to the key/certificates that are loaded/saved on the VPN pages
Even if I were to store rules to JFFS instead of NVRAM (which would mean that when backing up and restoring your settings, all rules would be lost), the max POST size for the web server could cause data to get truncated.
You should reduce the length of your Descriptions to make more rules fit within the available nvram space, or start using subnets to you can create rules in CIDR format.