I can think of questions where one tag would apply and not the other so I vote no.
For example life in a magical setting might have very little connection to biology. This all depends on how the tags are defined though. Does the tag life really mean anything? Maybe it should just be removed entirely.
One thing that's been discussed a few times though (and most people seem to agree) is that for the first month or two we should let tags go and see how they shape out. (Other than obvious cleanup like moon->moons or deleting design of course).
The word "life" has many meanings, so as a tag it may end up applied to a variety of different questions that do not benefit from sharing a tag. For example, questions on biology, longevity, lifestyle, magical lifeforce, rights of living things...
At the very least life will require a very clear tag wiki to make clear what it is intended for, but that in itself suggests that a different, less ambiguous word would be more appropriate.
I think the long term future of life is that it will be deleted. A vague tag eventually causes more problems than it solves. I'd like to see it deleted sooner rather than later, so that there is a space for new tags to grow into naturally, rather than leaving a much larger void later.