One of the main points of VACUUM is to protect you against XID-wraparound or multixact ID wraparound.So,your idea of auto-launch of a Vacuum Freeze is good but

One of the main points of VACUUM is to protect you against XID-wraparound or multixact ID wraparound.So,your idea of auto-launch of a Vacuum Freeze is good but i still believe it is important to be aware that you may lose your very old data if you dont do anything about it.