Yes I too hated the idea of having a partial build to finish and finding out I was missing a resistor or cap, to the point where I made sure I had every value available. You would laugh if I told you how many resistors I have now, so I may have taken it a bit too far but I've hoarded 217 unique metal film resistor values and 103 unique cap values, so at least I don't have to worry about not having something and I'll probably only ever need to re-stock up on the most common values like 1K, 10K, 100K, the rest will last me until I'm too old to solder
Stomp switches I order in 10s from eBay but usually have 20 to hand at any given time, same for 1590B's. I also have around 10 x 125Bs and 10 x 1590BBs for the builds that need them. For sockets I did a group buy with Aaron from Arc Effects a couple of years ago and got some really high quality open Neutrik sockets for a great price. I also bought 50 enclosed Neutrik sockets from Rapid Electronics so I had that type available if a build required it to save space.
I always order transistors in 100s if they are readily available in quantity. ICs in 50s or 100s from Tayda or GC Supermarket on eBay.
Because of all the stuff I've hoarded over the past few years it means that I don't really have to go on a big monthly electronics shopping spree any more, so it means I can just buy 10 more stomps, or 20 toggle switches, or extra boxes instead to get the stock of more expensive items built up too.