FWIW, I am hesitant to come to the SSD as a "solution" and agree with Bob. For me, all of my data files are on a 7200rpm HDD, and only the OS/X3/plug-ins are on my SSD (i.e. the engines). X3 will start fast this way, but I can literally choke it to death by piling on unnecessary things. I am also confused to opening several songs in the same project... just the overhead that implies seems unnecessary.
Project folders have made things simpler to find, and X3 can open multiple projects at once, so if I find the desire to move things between songs, I chose this route myself. "Lots of VST effects" can also put the chokepoint on your CPU rather than the data itself. For example, long ago I decided off the cuff to make a project with many VSTi's in it just in case I wanted to play around with them later, and when I opened that (blank project) later the load time was noticeable (and everything in that was on my SSD).
I would lean more to saving that project file seven times into their own project folders, then paring each down to only work with one song at a time. Of course you can open more than one at once, but then you will be driving that decision, not it being a "by default" setup.