I used to grab on to just about any kind of junk with electronics inside but have learned a few things. This was "free" junk, not something I'd have to pay for. Where I came out:
1. The junk takes up space - ok if you've got lots of it but most people are space limited. At some point you can have so many useful things that you can't find any of them - at which point most all of it is no longer useful.
2. Junk you have to pay for ties up your money. You might pay $25 for the welders and it's $25 you don't have to buy something else.
3. Items purchased new are usually pretty reliable, have specs, sometimes a warranty, etc. Something used could have faults and you may be lacking specs or parts identification. The odds are good that you won't be sure of what you've got and whatever it is might be bad. Worse yet is you use the parts in something then struggle only to eventually learn the parts were bad.
4. It will take some of your time to extract or recover the items or components. If you add that to #1, #2 and #3 you have space, time and money tied up in something that might be what you want and might or might not work.
Sorry for being so negative but I've eased off myself on the collection of things. The welders might be good if you can fix them or you know they have the parts you'll need for a specific project. On the other hand, if they were going to cost you $25 you might give some thought to the cost of the parts you might extract from them. The diodes you might recover certainly could be useful but if you were using them in a non-critical application you might be able to get the diodes new for a lot less.
What I do now with electronics - I might grab a power supply from a computer that is being discarded but only if I know my next step is to open it up and quickly extract the large caps, power resistors, marked power transistors and inductors. I can test those things and they are useful for experimenting. The rest goes back. I don't save the board with the hundreds of parts on it. I know I won't take the time later on to search. I use the space I save for an organized parts collection. While not as impressive I can find the stuff quickly.