I do 40 miles return for my commute and I can do that day in, day out, night shifts, day shifts whatever because I'm so used to it but it took a while before that was the case for me. Cycling 40 miles in one day is one thing (and I'd imagine that anyone fit enough to ride 10 miles, can probably ride 40 or 50 without a problem for a single day). However cycling 40 on monday, again on tuesday, again on wednesday etc takes time to get used to.
I imagine it'll depend very much on the terrain, and how "stop-start" the journey will be. If it's flat, and you can pick up a pace and keep it, I think you'll find it becomes doable quite quickly. Maybe not 5 times a week (certainly to begin with), but perhaps 3 or something. Just make sure you eat and drink (water) sufficiently during the day at work. A 10-15 mile commute you can "trudge" through a little hungry and dehydrated, but you don't want to do it on a trip like 30 miles - it will be very hard and unpleasant.
I eat again 90 minutes before I leave work in addition to whatever I've already had. On a day shift, I also stop drinking caffienated drinks by 1pm, and sip water throughout the entire day. That usually makes for a decent ride home.