Not too much to report. Timestamps has continued to run on auto-pilot. My "enterprise customer" has continued to pay me $10 per month to keep it running it cover my Heroku costs. In retrospect, decreasing their price so much was a bad idea.
To recap, originally I sold the subscription for $40 a month. Then I decided to make the whole app free again which made it a little awkward to have them pay, so I asked if they'd at least help me break even, which was totally fine. That was ~15/month. I suppose I didn't need to go quite so low, but truly those were about my costs, and I wanted to be honest. That was with the very expensive .fm domain name.
Later on, I decided to de-risk by moving to a cheaper domain (.me) so in case that customer decided to stop paying, I wouldn't be stuck with a $100/year domain to pay for no reason. After that change, I again decreased the price to $10 a month. Not sure why. Just to keep to the original agreement of "help me break even" I guess.
Anyway, things have been running just fine. Still averaging on the order of 3-5 uploads per day. Still no clue who these people are, since there's no login. And honestly, I still don't mind.