Best Answer Rob , 02 March 2013 - 05:56 PM
To answer your last question, PHP memory resources don't distinguish between frontend and backend processes. It simply provides the resources to handle any PHP functionality of your site. Keeping this in mind, we must consider that most functions of WordPress as well as PageLines, every plugin, section or process usually has a PHP process. This is why it's important to have more than a sufficient volume of resources available in the form of PHP memory.
Pingdom.com has an amazing service (free) to let you know if your site goes down for any reason. I'd recommend using it. Should you find downtime, you know you'll have to react and of course, plan a new strategy.
I went through much grief in 2011 with my site crashing frequently due to insufficient memory. It wasn't a technical issue, but one in which the pairing of PageLines and WordPress made my site so much more popular that too many visitors were draining VPS resources. Eventually, I discovered that moving to a dedicated server wasn't as expensive as previously thought and now, my site runs as smoothly as possible without any memory issues. Now if I could only get my laptop to be as cooperative! ;-)Go to the full post