Creak Advice

Got a noisy mountain bike. It's a down country full suspension 29er. The saga started with a bad rear wheel. Replaced the wheel. Fixed some noise, but it still wasn't great. Did the headset and the bottom bracket after that. Nice upgrades, but that didn't do much to resolve the issue. Took it in to get the pivot bushing replaced. Mechanic could do some of them, but refused to replace them all because they were seized (why he wouldn't drill them out, I'm not sure). Took it to a different mechanic who went through it it. It was quiet for about eight rides - not just quiet, it was silent. It's gotten warmer and the creaks of started coming back. This time, if it's warm at all I can get it to creak by bouncing on the seat -- so I'm convinced it isn't drivetrain. I'm thinking the rest of the pivots need to be replaced.

The question - should I keep chasing this or give up? If you don't count the wheel (it was worn and needed replaced anyway) I'm probably about $500 into this adventure. I don't want to keep throwing cash at a problem that will never get resolved. The fact that it was silent for a few rides make me think it is unlikely it is the frame (although it is much warmer now). The noise that it is making now is annoying, but it isn't the "OMG this thing is falling apart" noise it was before. It's kind of almost a click-ish noise.

Thoughts?