I counted it this time. First load (ever) of a game take 45 seconds or more. Subsequent loads of a game take around 20 seconds, before the first splash screen appears. I am using a modern SanDisk Ultra 64gb class 1 which was clean formatted FAT32 with 32k cluster size.
I updated twilight menu++ to the current version and there was no change.
One thing I can’t figure out is if I am using hiyaCFW or not and how this impacts speed. Been so long since I worried about the DSi I can’t remember what half of the stuff does. I have the hiya folder on my SD card, but I use twilightmenu. The ds-homebrew site’s description of hiyaCFW is confusing as fuck.