Interesting thread.
Different hobby, but in the radio controlled space I was in for a few years I found over-buying parts in advance caused issues. I would order stuff, sometimes in bulk, say buying 32 AA NiMh cells, then I discovered with a voltage regulator I could use much more convenient LiPos for that application, so I bought a bunch of pairs of those each and never used the NiMhs ever again. I still have a bunch of 2000mAh AA cells around, but they aren't even useful for clocks or TV remotes due to their lower 1.2 voltage and high dissipation they only last a few months.
The other issue with over stocking is that stock management comes into play. You order a whole assortment of stuff, use about 10% of it, then forget exactly what the other 90% was. 6 months down the road you need a particular component, either don't remember you have some or don't remember where exactly they would be and end up ordering more. Of course after you hit "Buy Now" at checkout you remember where the stock pile is. Battery connectors were an example. I think I ordered bags of bullet connectors three times and now have about 200 of them. Being meticulous about organising things into labelled parts trays and boxes would help, but that's not me.
Shipping cost tends to come into play and aggravate this. If you are ordering 2 x 555 timer chips the postage is probably more than the chips by an order of magnitude. You get a better price if you order 10 of them. So you spend an evening "magpie-ing" around the online store going "one of them, two of those, three of that thing" to lower the differential between cost and shipping. Then you realise if you order a few more expensive things you get free shipping. You spend £100 randomly. The stuff arrives, you flick through it and throw it in a box, happy with yourself. You don't use much of it for 6 months and then have no idea what you actually have or where you put it all. So you order it again.
I have plastic tubs and boxes full of RC electrical parts, high amp connectors, low amp JSTs, servo adaptors, battery charge adaptors and splitters, load testers, volt/ammeters, discharge loads, wall warts, you name it. Most of it still in the plastic bags they came in.
Case in hand.... my ExTech multimeter hasn't arrived yet. I did some bread boarding yesterday, building logic gates from transistors, figured I must have a volt/amp meter somewhere for RC stuff, but couldn't find anything after an hour going through boxes of stuff.... I'm sure it's there somewhere though..... back to LEDs, trial and error, and screwing around with my phone camera on zoom to read resistor values. Still managed to successfully build, ANDs, ORs, NOTs etc. Though I nearly cooked a few transistors and without a multi-meter couldn't tell that I was driving the full power supply current though the base of the NPN. No NPNs died though.
Yet, I don't learn my lesson. I'm currently looking at assorted part kits. Like a 2600 piece resistor pack. 1000 piece cap pack and still trying to find a sensible assorted pack of logic ICs.