I believe Epson's Mac Driver is also limited to about 37".
Many "RIPs" bypass Epson's driver and are not subject to this limitation. I have done longer prints on my Mac using the ColorBurst RIP that's bundled with the Graphic Arts edition.
Beware: the 3880 isn't designed to handle very long sheets of paper. The built in guides just aren't designed for sheets over 3 feet long. Personally, I worry about paper skew. When you double the paper length, you double the impact of any paper skew.
When cutting your own sheets from a roll, you need to be careful to get a straight cut, and to get the curl out of the paper.
If you routinely print longer than 37", the 3880 may not be your best choice.