I just started an upload of 100k files (1.74 GB in total) and the first 5k files took 05:37 Minutes. Sync client estimates it will need ~2h for the other 95k files.
oC client 2.3.2 runs in a VM with 2 virtual processor cores and 2GB of memory, with regular DSL internet connection.
oC server 10.0.3 runs on smallest Digitalocean droplet, but this won't be enough if multiple user would access the same oC instance.
If your upload takes days, you need to check for bottlenecks on the server side.
ownCloud plans to support HTTP2 on the server and in the clients. This will bundle many small files to improve performance: