After inspecting the source code and performing visual check, I found that GMail is adding free space at the rate of 0.000004 MB per second.
Which means per day GMail adds 0.3456 MB (0.000004 * 60 * 60 * 24) and per year 126.144 MB (0.3456 * 365).
Is this free space increase sufficient? Depends on you! For guys like me buying additional storage from Google seems like an inevitable future. But for people with less mail activity this free space addition shall be more than sufficient.
By the way nice PR Google!
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