Last week was a productive writing week. I got writing sessions in on Tuesday, Wednesday, Thursday, and Sunday. I think that might just make up for the whole week I took off while I was on vacation. Almost.
I've made good headway on the next Sally Prescott adventure - wrote a couple more scenes, added in a new plot point for future stories, and outlined it through the end. I think I have three, maybe four scenes left to write. If all goes well, I will finish writing it this week/weekend. It needs a lot of editing work, so it won't be ready to post for awhile yet, but it'll feel good to actually have it written. Progress!
I also finished writing my Doctor Who fanfic story on Sunday! I am not really an avid supporter of fan fiction - is it really worth it to spend time writing something that you can never publish? - but it was hella fun to write. It actually turned out rather well, I think.
Sunday was absolutely amazing, though. I haven't spent several hours in a row doing nothing but writing (with the occasional trip to the bathroom or kitchen) since Nanowrimo last year. I'd forgotten what it was like to get so lost in writing that you have no idea what time it is, but being so excited about what you're doing that when you look up and it's been four hours, you don't even mind.
So I guess to answer my own question: yes, writing fan fiction is worth the time. Sometimes you just have to write because it's what you love to do.