Priming ahead of time

Is it a good idea to prime cases and then store them ready to load when you need them, or should you only prime immediately before loading, or does it matter not a wit?

I usually prime just before loading, but it probably doesn't matter.
If I primed earlier the cases would go in the cupboard next to where the packets of primers are, so similar conditions, though I do keep my primers in an insulated chilly bag.
I had some rounds I loaded back in the mid to late 90's that I pulled and emptied a year or two ago. I fired off 50 of the primed cases last week - no misfires or hangfires, so I consider that a pretty good test.

Cool, thanks, that's what I'll do - store them with the other primers. I just find it's more time efficient to have primed cases ready to go.

I often have primed cases stored & ready to load & found no issues with what so ever sitting there sometimes months on end.

It just helps me for time efficiency when it comes to powder weighing & bullet seating!

I find spiders in cases that have been prepped and sitting around more of an issue.i usually prep and prime all at once them load as needed.

Primers are relatively stable, moisture or oil is what you have to worry about. If you keep them clean and dry loaded in cases for decades they would probably be fine.

I prime ahead of time with some cartridges, sometimes years in advance and then store them in sealed plastic containers with dessicant packs with a sticker on them, "ready to load".

You'd think that if you could store primed cases under the same conditions as your unopened primers they'd be fine.
I keep my primers in a fairly warm even tempertatured place and in a big ziplock plastic bag.
I reload in my garage that's a bit damp with themperature fluctuations (condensation) and dodgy for primer storage, so I try to do the priming same day or at most 24 hr before if load powder and projectiles.
I store my empty cases in snap shut plastic case boxes to keep spiders out. Also lay a paper towel over them while throwing powder so insects don't singe themselves on the light bulb and fall into the case. :)

I size,prime, and store cases in sistema plastic containers.

To me, it's the ideal place in the loading sequence to stop, until I either need to load more, or decide to change my loads.

Makes loading quicker when it does need to be done.

My empty cases are stored in plastic ammo boxes labeled with calibre.
I always try to do all the brass prep up to but not including priming in one go, and have a label inside each box with number of firings and "ready to load" written on it. My usual case prep is inspect, tumble, deprime and size (usually neck collet die), check for length, clean primer pockets, camfer and deburr. I do sometimes inspect and tumble the cases then leave them, my main preference is that if a case doesn't have a primer in it it should be ready to load.
Cases needing trimming usually get put to one side as its often only a few each time.