Sorry for the late reply I didn't get notification for this post. I do not put any limit of save files, and all of the file previews get loaded at the time you access the menu. The problem usually was not noticable on a better rig, yet it was a problem because of newtonsoft library which allocates lots of garbage. That library is now only used for old saves, because the save file system was internally refactored recently.
Thanks for playing. For quicker reply message @hikkeiru on discord.