What computer operating system are you using and have you updated 12 to 12.1 using an opened project's Help Menu/Updates?
The burn time is going to depend on the complexity of the Timeline structure and content as well as the computer environment.
Have you applied video stabilization to any of the Timeline content? What is your burn to - DVD-VIDEO on DVD disc or AVCHD on DVD disc?
The following quote from the Adobe Document Adobe Premiere Elements Help | Sharing to DVD on this type of question might be of interest
Compressing video and audio for use on a disc is very time consuming, even on high‑end, dedicated systems. The time required varies depending upon the speed of the computer processor, the amount of available memory, and the complexity and length of a project. A standard video project of 60 minutes may take from 4 to 6 hours to burn. Many DVD Disc producers burn a project overnight.
Windows 7...Burning to DVD Disc. I will update and see what happens.
We will be watching for your progress.
The major perk of the 12.1 Update is that it fixes the text style error which occurs in the Expert workspace only. These version updates contain obvious and not obvious benefits. So, it will be interesting to see if your burn to disc times will change after the 12.1 Update. I think not, but let us see.