Thumbnails not cached?

[Marlby23]

Hi, i've been a happy TC user for many years.

One thing i began noticing more is its thumbnail behaviour. I have configured TC to use IrfanView for thumbnail extraction and lister usage, but whenever i open a folder full of images in thumbnail view it appears that the thumbnails get extracted again.
This is specially noticeable with .CR2 (raw) images (I have the line "IviewAdditionalTypes=*.cr2 *.nef" in wincmd.ini to view the thumbnails inside TC)

Am i missing something? The file tcthumbs.idb is growing in size but the thumbnail loading time is pretty much the same if the program doesn't use it. Thanks.

[Horst.Epp]

I'm using Imaging x64 lister plugin and the cache is definitely used.
There is a noticable time for the first visit of a large picture dir
which is no longer there for the next visit of that dir.
Don't know if Irfanview is the culprint, I like to use lister plugins.

[Marlby23]

I tried using Imagine lister plugin, but reverted to IrfanView because it's unable to render Canon RAW (*.cr2) files.
Maybe TC doesn't cache non standard image file thumbnails even if it displays them?
Other formats apparently get cached, but still TC takes its time to display them whenever i scroll the panel. This doesn't happen with other viewers which use cache, such as XnView thumbnail browser.