The is sometimes referred to as a LRM, or long-running molecule.
If you look at the graphical screen on your UD Agent (the second button with the "i"), you will see in the top left corner. The current molecule that the program is crunching. The number at the end represents the interation of the molecule. There are 100 iterations per each molecule, and the last set tells you what number you are on. So if it is at 16%, you've got a long way to go. If you are at 93%, you're almost there.
There really isn't any way to tell how long a molecule will take. On the bottom left of the same screen you will see the number of conformers. This can be anywhere between 1 and over a million. If you have a molecule that requires a lot of conformers, then it is going to take a lot longer to process than one that doesn't.
Unfortunately, you have to wait it out. If you stop, you lose the processing time since your last save (when you have finished all of the molecule iterations and move on to the next), which is each %.
There are a couple of ways to tell how much time you stand to lose if you need to shut down, etc. One is to look at the datestamp of the file in the ud directory on your local drive.
The other way is to use UD Monitor, a third party app which lets you know how long it has been since your last save (as well as being able to cache multiple jobs).
More info can be found at the UD Forums.
-Tacks