RP's only die if you let them. LoR went on for four years. It had its ups and downs, but we kept pushing, and made it to the end, and now, to the sequel. That's not being harsh or elitist: Sometimes I let RP's die. Without even meaning to, even.

That being said, here's a few solutions I'm shotgunning out to help as a veteran GM. :sun

[b]Rebirth:[/b] A drastic measure, you reset the RP's timeline to a previous point, perhaps all the way to the beginning, and explore a different path. If you want to intersect back to the main path, create multiverse theory. This can very well by itself become very complex to keep track of though.

[b]Autoresolve:[/b] Just like how strategy games often have autoresolve tools, you can autoresolve a plot and move forward to a new plot with the same characters. Especially effective if the characters are the element you want to save above all else, but can feel jarring.

[b]New Goal:[/b] If you don't want to rebirth or autoresolve and move to a different plot, then drop the characters into a new "zone". Maybe they were kidnapped, crash landed, got lost, etc, but put them in a new area with a subplot that you can tie into the main plot at some point. During this time you can adjust the main plot, making minor retcons here and there until it becomes interesting again.

[b]Carbonite Bath:[/b] Hibernate your RP for a month or two and come back to it. You may want to retcon a few pieces of it once you come back, but sometimes a break is simply all that's needed to give an old idea life again.