However I'm surprised to see you still have many promos in your collection, Mark: Is it on your priority list to upgrade these with stock copies? (and where do I have to queue for your spares?)
I started collecting in the mid '90s, when I bought a collection of around 700 garage 45s from Jules Normington, who used to own Phantom Records here in Sydney. His collection/store stock had been picked over by other collectors long before I purchased the remnants, and there wasn't much left. The most amazing thing as far as I was concerned, was a copy of the Chessmen "I Need You There" on Bismark. It goes to show that it must have been quite common at the time, if all the other collecting guys from around the world didn't want it.
At the time, I actually thought that the collection was incredible. But it was basically a collection of things like Knickerbockers, Standells, Seeds and that kind of stuff. And a lot of the records were promos, not so many stock copies. I also started using the internet to scour for other small, reasonably priced collections to add to my stash. But it wasn't until I hooked up with a couple of avid and very knowledgeable collectors here, that I realised that there was another level of stuff out there. Via these friends, I was introduced to some of the heaviest US collectors operating in the 1990s. They started to offer me top flight items they had to trade, and in some cases, from their own collections. Stuff like the Chob on Lavette, the Barracudas on Zundak. Stuff that cost as much for one record, as I was spending previously on 100 records. But I found the kick was 100 times greater as well...
For the next 10 years I concentrated on the absolute hard core of '60s garage collecting. I was not particularly interested in replacing my promo Music Machine 45 with a stock copy, in this supercharged world of high end collecting. My thinking was that I could get those common records later, but if I missed out on The Keggs or the Four More, there would probably never be another chance.
I have obtained quite a few stock copies over the last 10 years, but I've still got a long way to go compared to Moptopmike, or Barry Wickham, who both have fabulous collections of stock label 45s (so I've been told). But, I found that I didn't want to let the promo copy go, when I got the stock one. I became one of those retentive collectors who has to have both, haha. So, don't stand in that queue for too long Greg!
A point to make is that not all 45s were ever released as stock labels. For example the Tropics on Laurie, and the Rooks on Mercury shown above, only ever came as promos. And the other point is, sometimes the promo actually looks better with the sleeve. And the last point - in theory as Patrick the Lama has pointed out, the promos were often pressed first, and therefore theoretically have superior sound quality.