Assuming your computer has a replaceable battery, which is not the case always. Replacing a $80 battery is worth it to avoid stress, but replacing a $2000 ultrabook may not be.
Even if it's not made to be user-replaceable, surely it can be replaced by someone with the right skills and tools for much less than the full replacement cost of the entire device.
I would think your ultrabook would be past its manufacturer's warranty anyway at that point anyway and would be a candidate for some sort of DIY battery replacement.
