Is it advisable to submerse them in slightly soapy water until I get time to wash them, which could be a couple days in the future?
The only things I treat special before washing are spoons/bowls used for oatmeal/cream of wheat and dishes/flatware that have egg yolk on them. These are the items that I find do not come clean in the DW if they sit with residue on them before washing. All I do for them is to rinse them right after use. If the residue has dried on them, then I just soak them for about 5 minutes in plain water to loosen the residue, then give them a quick rinse before loading in DW. I don't fill the sink to do this--I just fill the bowl with water and soak the spoon and bowl at the same time. The same technique works with pretty much any dried on residue on my pots and pans too, but I try to wash those as I go.
Hope this helps!
I don't do anything specific to flatware ... load it / collect until a full load accumulates.
Acidic food residue can cause pitting in some cases if left long enough.
Do you have a dog?
Sure, you can put the flatware into a glass filled with soapy water and let it sit. but it will get gross in a few days. I usually just leave mine alone and spray them just before I put them into the machine. The spray knocks off the 'big stuff'. Just a few seconds, not a whole production.