importing is about CPU and MEMORY.
you might get a small benefit delaying the index update using
ALTER TABLE YOURPREFIX_dataitems DELAY_KEY_WRITE =1
however this might result in corrupt indexes whenever your mysqlserver goes down unexpectedly so you need in your my.cnf:
mysql can be optimized a lot, however most of the optimization applies to SELECT not to UPDATE.
best thing to do is run the import as cron job, then time is not that much of an issue. Only thing i encountered is that the database connection disappears depending on the time-out settings.