Sounds like you need Event Manager X ............... the best $4.99 I ever spent.
As I'm in the UK it was something like £3.50 !
You should also be storing your projects and events on an external hard drive and not the MBP's internal one.
I bought it and the start up and managing projects / events certainly has sped up, but the rendering issue is still there.
Here's what I ended up doing....
I bought that app you suggested and I am going to use it, it's great.... But what really helped is turning off Background Rendering. That was sucking all the life out of my computer.
I don't keep anything on my computer, but on a Lacie T-bolt dual hard drive....
Yes, a lot of people swear by turning off the background render, though I've never really noticed any difference.
I don't know why it slows things down because theoretically it only start up 5 seconds after you stop editing and shuts down the moment you continue ................ maybe it still continues rendering at a slower rate.
In theory this is true, but in practice it's real anchor in processing.
The app is constantly triggering / de-triggering the render function, which taxes the processor.
I'm really close to going back to Adobe Premiere pro again. I just get the feeling that APPLE isn't focused. Before I updated to the latest version of FCPX rendering was faster, so all I can assume is in the update somewhere, things went foul.