ROMs A battery thin, "travel rom?"

My phone gets about 12 hours if I turn off the data and put brightness down. It's running liquidsmooth. Samsung skyrocket.

I'm wondering how much extra battery life I could squeeze out with a custom rom. Is this a thing people do? A really restrictive ROM with just phone and extremely limited browser capabilities, and a kernel that lets it extend battery life? Something I could flash before a weekend trip out of town, and leave my cord behind?