I think we both understood after the first week together there that our non-refundable return tickets were just a waste of money, and that we had to stay there for at least to months to max out our visa.

Good to see you're not caught up in the "sunken-cost fallacy", it's not abnormal to think that if you've paid for something, you need to utilize it.

Personally I have this year-pass to the transport in Oslo, I haven't utilized it much during the last couple of months ... too good biking weather :-)