'5347 in 10 hours' is kind of meaningless without knowing how big each file is, both in minutes and size/bitrate. If each file is a 1h concert then you're doing fine...
Is your collection connected directly to the MC computer (via USB or internal disk), or is it on a NAS connected via Wifi or LAN?
Napkin math: 5000 tracks, 5 minutes per track, ~60 MB FLAC per track, that's 300 GB of data to read; if you're converting to 320Kbps MP3, that's about 100GB to write. So, 400GB in 10 hours, that's about 11 MB/sec of data being transferred, or around 100 Mbit/second. This number rings a bell...
So, you might be limited by your networking. If you're on a 100Mbps cabled network, you can't go much faster. If you're on Wifi, switch to cabled or try moving things closer to the Router or Access Point.
If you're using USB or an internal disk, then the issue is something else, as 10 MB/sec is not that much for a directly-attached disk. Check the CPU usage to see if it's pegged at 100%.