Goto /etc/logrotate.conf and define rotate in odoo conf params.

rotate count:- This specifies the number of times to rotate a file before it is deleted. A count of 0 (zero) means no copies are retained. A count of 5 means five copies are retained. 

eg:rotate 12

if you define weekly on conf and rotate is 12, 12 weeks logs can be retained.

instead of week you can also use, yearly, day, monthly

Here is an example of odoo logrotate configured:

​/var/log/odoo-server {
    monthly
    create 0664 root utmp
    rotate 12

}
​