There's a limit of 256 folders in yout Pose directory. Any more than that and they will stop working. There's no harm in deleting stuff you never use but it may be safer just to move them. I use an extra 'Pose Archive' folder in my runtime. Anything not currently needed gets moved into that and moved back to 'Pose' only when required.

Expert in computer code including, but not limited to, BTW; IIRC; IMHO; LMAO; BRB; OIC; ROFL; TTYL. Black belt in Google-fu.