Tvheadend

Hi,
I have just noticed that I have about 130 000 files inside my .kodi/userdata/addon_data/service.multimedia.tvheadend.save/imagecache/meta/ directory under Openelec 7.0.
Some of these files are quite old (my recordings are deleted when free space is needed). Are they supposed to be automatically deleted? Can I clean them?

Many Thanks