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The investments examples you mention typically have up-front and fixed terms for the APR, etc. So these would be much more analogous to the other kinds of PoS models I mentioned in the previous post--both are geared around a more steady/predictable annual rate-of-return. As explained, the TZC PoS model is truly variable depending on network factors and other conditions--like most PoW. So while you say that the savings/CD model is "the closest analog to staking coins", I would argue that its the other PoS model--i.e.,
x% PoS--you would need to compare to in order to make that claim.
That's my take on what (I think) you are saying.
But perhaps I misunderstood--feel free to clarify.

Hmm, I think I see your point of view now. Guess the trap was sprung on me!
I was going to argue that the wallet itself should provide an estimate of the time it would take to receive a block reward from staking because it has all of the necessary data points to do the calculation, but I can see how it would be self-defeating if that number wildly changed as a result of receiving/sending TZC - ie, using this as an everyday payment method. However, I do think a web-based calculator, officially provided by the dev team, should be a priority as staking is a primary function/feature of TZC. In fact, one of the main reasons I am mining it right now is to have a decent number on hand for staking (because, let's face it, there isn't much ability to actually use cryptos for everyday transactions just yet).