Just on a side note for the non-native speakers: shouldn't it be "API half-lifes" (as 'half-life' in terms of radioactive decay) instead of "half-live" or am I missing out the idea of the headline?
life -> lives
wife -> wives
elf -> elves
half -> halves
leaf -> leaves
chief -> chiefs
brief -> briefs
Maple Leaf -> Maple Leafs (Canadian Hockey team)
Rather than throwing up your hands in defeat and saying, "The English language is totally inconsistent; the only way to learn it is to memorize each arbitrary word form," the key is to familiarize yourself with these patterns so that at a minimum you can make a better guess next time.
Hopefully, WA learned today not just that the plural of "life" is "lives" but that, in general, when a noun ends in -f or -fe it usually changes to -ve. So if tomorrow he sees a sign that says "5 loaves of bread for $1" it won't catch him off guard like the title of this submission did.