Martin,
I think you will be OK no matter how much you import. As I said earlier, I think you can be huge numbers of MBs in the folder without any degradation of speed or performance.
Just for kicks, I imported a 25GB file, which actually did get imported. I was able to easily open that file and a 2KB file from within the chart.
I thought that maybe it would be slowed down since Access usually sends everything over when a query is done, but it didn't seem to affect it.
