It's not the time that's the biggest issue here, it's the documentation. Since around the time of the i945 chipset, Intel has stopped sharing data crucial to coreboot development, mainly the location and configuration information on the memory controller registers, these docs are now only available under a very high level NDA, possibly internal-only. This is now stuffed into their MRC code and part of a binary blob.
For this reason, coreboot is mostly aimed at AMD-based systems these days. AMD has been very supportive of the coreboot project.
-Corey