Seems reasonable - or renew it, pm them one more time saying you had to renew it, please cover my costs, etc. Then make a public announcement stating the facts, that you were going to give up after this last announcement & keep it?
Drop that domain!
DONE
Why would you drop it?
Most of us that have been around awhile have had this happen more than a few times. Unless it was an under $100 sale, I'd pay the renewal a couple times. An added bonus is that it may continue to earn parked revenue.
I had a guy buy a domain in 2000. In late Sept 2001 it came up for renewal. He never completed the weird procedures the registrars had back then (every one was different).
I paid for the renewal because I felt it was the right thing to do although I sent several emails and one snail mail to him and received no response.
At the end of October 2001 he got back to me. I'm glad I did what I did. He had spent the last month-and-a-half combing through the ruins of the South Tower looking for remains, including that of his sister. He was grateful when we finally straightened out stuff later after things settled down.
Many of us have resold domains a year or two later after we renewed domains because the buyers never fully completed the transfers on (through no fault of our own).
I see no reasonable reason to drop a perfectly good domain I already made a good profit on once before.
Majority agree dropping it is the best way to avoid future disputes!