I ran update-all tonight and checked some new options, such as "Arcade ROMs Database" and "Unofficial Cores". I then ran a few Arcade cores such as 'Congo Bongo' and 'Street Fighter', but upon loading the Mister paused for about 30-seconds before finally loading into the core. I tested console cores and the loading was instant. Is there some setting I'm missing, or have Arcade cores always taken about 30-seconds to load and I'm going senile?
The Countdown Timer option in the Update All Settings -> Misc Menu affects how long the script will pause before proceeding with updates, this is to give you a chance to enter the settings menu and has no bearing on how long it will take to load a core. You'll observe some arcade cores take longer to load than others depending on the number and size of assets, since you're not only loading the core logic itself but also game data (graphics, music, etc.). Console cores load quickly because they don't load any game data by default.