I've also experienced a range of times. My mom sends me packages and always emails me when she ships them so I can keep an eye out. Sometimes I receive them in a few weeks but other times, it's much longer. I think the record delay was for an Easter present - I got it in the end, but in late summer!
To be fair, the same happens to me when shipping UK to US. I've had some packages arrive relatively quickly, and others seemed to take ages.
This Christmas, I didn't take any chances. I shipped via DHL and IMO, it wasn't horrifically expensive. I dropped the package off at a DHL service point on Saturday, it was shipped on Monday, arrived in the US on Tuesday, and was eventually delivered to my family Tuesday afternoon.