My commute distance increased from about 11 miles (18 km) to about 16 miles (26 km) each way about five years ago. Initially I thought I might not be able to continue commuting the longer distance but decided to give it a go. Although my commuting time increased by about 20-25 minutes, it didn't feel much more physically demanding, and I have continued bike commuting at about the same frequency as before the move. My commute route is very hilly, but not extremely steep and the longest climbs are about .5 km.

If your commute is mostly uphill in one direction, then it will be a very easy ride in the other direction. Give it a try. You might find that it's not as bad as you anticipate.