Since I started to capture timelapse sequences the number of pictures in my lightroom catalog increased very fast, by now 150000+. After rendering usualy I delete the temporary jpg-sequence but keep the dng's for future use.
I realized now that lightroom is getting slower and slower, is there a recomendet limit for catalog size? Do you have the same problems?

I have a similar size, no problems at all. And also from my experience, catalog size has very little impact on Lightroom Performance.
If you have doubts about that, you can try to create a fresh catalog, just import a couple of timelapse sequence (they will get all their editings from the XMP files) and try if that helps.

The JPG or TIFF intermediary sequences have no impact on the catalog at all, because they won't get imported.

Working with DNG in general lead to a slower workflow - if your camera shoot native raw, I'd recommend to use it in the future and not convert to DNG.

Regarding your current catalog, you might want to let Lightroom optimize it, there is a feature for that when backing up the catalog.

In any case you should turn off any indexing, smart preview generation, face detection etc. in Lightroom Classic.

Hi Gunter

Thanks for your fast answer.

Does DNG slows down the workflow in general (if so do you know why) or just on import, when converting?
Catalog optimizing is done when the backup runs.

I found out the my camera saved JPG&RAW, I've deleted all duplicate JPGs now, but I'm not sure about influence on performance.

Where do I turn of indexing and smart previews?

DNG slows the workflow, because Lightroom insists in writing Metadata inside the DNG files (and not sidecars). Both, LRT and LR will read, whichever is newer (sidecar or embedded). But nevertheless this will slow down writing of the metadata in LR and Reading in LRT. Apart from the additional step for converting.
Also if you do backups, those will also be slower, because when you edit something, with normal RAW files, those won't change (only the XMPs) but with DNGs the whole files will change because of the embedded XMPs changing.

Additional JPGs shouldn't slow down anything, they will be ignored by Lightroom. But I'd also remove them. If you use the LRTimelapse importer, there is an option to skip such JPGs directly on import.

Thanks for the explanaiton, so DNG's are slowing down the LRT workflow but not LR in general (only while convert).