I have the same problem. Long-running romance series aren't my thing, but non-yuri titles with actual yuri, not just subtext, are hard to come by. I'm assuming you're already familiar with Bodacious Space Pirates, Poor Poor Lips and Steven Universe?
Personally, I ended up settling for stuff with strong subtext, as long as it isn't played for laughs, and shorter yuri manga. But good luck with your search!