Cache image thumbnails generated in Controller (not in template)

Questions
1

Silverstripe 4.x

When I resize images via a page controller, the thumbnails only seem to be cached for a small amount of time. Is there a way to properly cache these?

$image->ScaleHeight(1080)
2

I don’t think the resampled image file is generated until you call e.g. $image-> ScaleMaxHeight(1080)->Link(). In my experience, once generated they persist indefinitely.