The plugin hasn't been updated for a while, sorry about that but don't have as free time lately.
Though the plugin supports most of Luxrender features.
I plan on updating the exporter when final version of Luxrender 1.0 is ready, so as to gather any changes and work on them altogether.
Also im happy to see that luxmax works with 3ds Max 2013 without recompiling it
Now about Luxrender performance, you can write on the main forum and post your render settings and scene details, so as to get feedback and see if you have done some overkill with the settings or materials.