I wouldn’t say they take longer. Oysters in general don’t take long and colonize rapidly.
My GS-jars for example took less than a week until I put them to substrate.
It mostly depends on the genetics, more specifically, the senescense. If the culture you got is a bit older, it takes longer to grow and is more prone to contam. This time I got lucky, but often, many growers “cut” their LCs, which results in too many cell divisions.
That’s why we work with culture slants. I don’t trust my supplier enough to give me fresh specimens, and therefore I try to get some of them fruiting, take spore prints to reset the genetics, and then grow from them. When I’ve done that, I back up the culture in my fridge until I need to use it again.
This guarantees me to get super low P-values, resulting in strong immunity and growth, which I strongly need, since I grow in unsterile environments.
Also, if something goes horribly wrong, I always have backups. I learned from my past mistakes…