Hey glocke, your thread is timely, because I was looking for the thread that talked about Optima Gold strings (it was closed back in May '10)...At that time, I had just strung up a couple of my basses with the OG's and was very pleased with the sound, and I'd heard that they stayed bright and new sounding for a long time.
Well, now it's been 6 months and they still sound about 80% new...and I've been playing nearly every day on them. Although they're expensive, they have lasted much longer than other sets, so for me, they are actually more cost-effective over time than other sets.
Good luck with your string search.