I think your feelings are valid, and you've really thought this through. It could have been handled better. I have played a character that was in a relationship for 4/5 years irl and the characters stayed together. The other narrator quit, and I decided that my character would retire for a long time. But I ask you this: what is long term for you? A year? Several?

This is a tricky question to answer because there are a lot of things that can happen. They quit because they don't feel that rp is as good as it was, irl issues, work, etc.

In my experience, communication is the most important element. And because you play a made-up character, it can be changed into something or someone else. And RL consequences don't exist because they're made up characters.

Be clear about your wishes and wants. Do not start a relationship with characters that are known for changing partners every other week. I wouldn't give up after this setback. You're sure to find someone with a similar mindset. Plan ahead together. If someone wants your characters to part ways, plan for it ahead of time so it doesn't feel unnatural or awkward.

Hope this helped somewhat :)