There is little point in stocking up with a workshop full of components and designing your project around components that you have had in a drawer for 5 years as things may have moved on.
I somewhat agree and somewhat disagree (this coming from a guy who will probably never use the MAX232 chips sitting in a drawer downstairs because... I've moved on from RS232 for projects). For specialty components, I totally agree that you should probably just order them on an as-needed basis. It is pretty handy though to have a bunch of "jellybean" components around that you can just build and test with. Cheap enough that you don't care a whole lot if you hook them up wrong and let the smoke out, and generic enough that they'll probably "just work".
For projects that are doing "hard" things, absolutely there are probably parts that exist that will hopefully match the requirements. There's also a lot of projects and prototyping work where almost any part will do. LM324s, TL08x, 2N2222/2N3904/2N3906, LM317, etc. For me, as someone who doesn't necessarily have a whole lot of spare time to hack away on electronics projects, it's really awesome to be able to conceive of an idea for some little thing, sketch out a schematic for it, put it together on a breadboard or home-etched PCB, and have something neat working by the end of Saturday afternoon. Jellybean parts definitely facilitate that.