Could you try and employ an R or Python package to import the Excel file and see if that could help.
Also, you could try to use R to store the data in a ‘portable’ format like SQLite that KNIME might then be able to read back in. But like @ipazin suggests: make sure you have the necessary recourses ready. And from my experience more factors can play an important role when it comes to the performance of imports:
- hard drive (SSD vs. HD)
- aggressive virus scanners
- virtual drives and LAN connections (even if the IT guys promise you it would work ‘just like a local drive’)
Do the excel files contain ‘regular’ (table) data or are there large graphics and stuff inside.