what Beth said.
My ride to work is ~13 mi each way, and it isn't that bad. In fact, after you've done it a time or two it gets easier. I think just being so familiar with a route makes it easier to ride that the same distance on any other route.
I can barely ride 25 miles, but I can easily ride 13 miles twice in one day, with an 8-9 hr break in between.
If you can bring your cloths and things to work the day before, then you won't have to carry much. If not, then as Beth said, make sure you know how you are going to carry everything and how it will affect you.
I'm going to ride at least 2 days that week, maybe 3 if I can.
have fun!