Mag 12 2014, 13:19
Do it often.
Last.fm will only accept the last 10 days or so of music, so you'll lose anything older than that.
Unless you recalculate the dates from a recent point in time.
Then you'll import 7 months worth of music what looks like 10 days. Great for fucking up your last months stats! But hey, at least the 6 months, 12 months and overall ones will be closer to the truth, right?