Would there be any drawback to running the following commands via cron every hour or so as a way of improving performance?

service mysqld restart

service lighttpd restart

service network restart

I am a newbie and I know this question may seem silly, but these commands help quite a lot to reduce memory usage when I start to go into swap.

Running CentOS on a linode 360 with kloxo and two magento installations running 3 stores. I know magento and kloxo are resource intensive, so if anyone has any better suggestions please let me know.

No, it won't help at all. In fact, it'll probably break things if somebody tries to access your site in the meantime.

What you need to do is to configure the individual services (e.g. my.cnf) to prevent them from using excessive RAM even if left running for months at a time.