Keeping log files

We want to keep all log files. This presents two problems, space and rotation time. To address space I want to compress the log files (bzip2). To address rotation time all I can think to do is not rotate and instead use cron to periodically rename (with the date), and compress the log file. My concern is how to safely get the existing logs and start from scratch without potentially loosing log entries. If I copy the log file and then use /dev/null to clear the existing file, then there is a window between the cp and the /dev/null. If I move the file will a HUP sent to auditd break the connection to the old logfile and start a new one? Has anyone else done this? Is there a better option than the ones I've listed here? Thanks, -Mont