Do you have any reasons other than having a somewhat decent idea of how much time you have left? Battery power doesn't work on a time basis as power expenditure isn't consistent.
>Battery power doesn't work on a time basis as power expenditure isn't consistent
It can be quite consistent if you do very simple things (CPU-wise). SSH-ing into servers and working on them all day is pretty consistent in battery life on my MBP.
My power expenditure is consistent: Most of the time when I'm on battery I'm typing in Scrivener, which leaves CPU use a flat 0%. (Presuming I've remembered to SIGSTOP Chrome.)
The battery life indicator was reliably accurate. I miss it.
It can be quite consistent if you do very simple things (CPU-wise). SSH-ing into servers and working on them all day is pretty consistent in battery life on my MBP.