No, its not, because you can't trade in a cert unless you'll end up having enough to buy the next cert you want.
If I want to get HA, and forget CE and Inf alltogether, I have to choose which one I want to waste for 24 hours and which I will keep (pretty much being a waste without the other i am forced to forget). You should be able to forget both at one time, then get the 24 hour period.
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