I definitely see your reasoning here. You are saying that if a "day" in one place is symbolic of a period of time, then a day in another context also must be a symbolic period of time. You are essentially arguing by analogy. In other words, the means of interpreting day must be analogous in every case.
The problem with this is that no one will be able to sustain this argument across the entire Bible. Bottom line, argument by analogy is a logical fallacy. Each case must be taken on its merits. When it says that Jesus went out into the desert for forty days, I assume that all or virtually all Bible conservative Bible interpreters take those forty days to be literal. I assume you do as well. Yet you interpret the weeks of Daniel to represent sets of seven years. They are not literal days. So do I. I also believe that the days in Genesis chapter one are most likely metaphorical references to indefinite periods of time. Whether a particular description in the Bible is to be taken literally or symbolically must be taken one case at a time. Some say we must always take the Bible literally, but these people cannot possibly maintain this view. God does not have a hand and the Pharisees clearly were not a literal brood of vipers. The rules of Biblical hermeneutics apply in every case. The context, the background, the mode of literature and other factors are used to decide whether a description is to be taken as literal of symbolic. Yes, you can have it both ways. The Bible is sometimes literal and sometimes symbolic, even in using the same description. The lion who attacked the children who called Elisha was a literal lion. The lion in Daniel chapter eight is a symbolic lion (representing Babylon).
So, the weeks in Daniel chapter 9 must be taken on their own merit, as must the days in Genesis One. Yes, I can have it both ways. The only question to be asked is what is the most reasonable interpretation of the passages at hand. I already justified my interpretation of Daniel 9 and Genesis 1 in the Q & As you refer to. If you disagree, please explain in each case why you disagree. I have already stated in great detail in both cases why I reach the conclusion I do. If you want a more detailed explanation of the weeks in Daniel 9, you can read my book Daniel, Prophet to the Nations. If you want a more detailed explanation of why the days in Genesis 1 are most likely a period of time, you can find it in my book "Is There a God?" (www.ipibooks.com)
Bottom line, I disagree that the last week of Daniel 9 is a future week of tribulation because it does not fit the passage well at all. The last week of Daniel 9 is the "week" that Jesus came to Jerusalem. It was capped off by the events described in Daniel nine, including the surrounding of Jerusalem, the destruction of the city and the abomination of Desolation being done on the site of the temple. All of this was fulfilled in striking detail (as was prophesied by Jesus as well in Matthew) in AD 70 when the Romans destroyed the temple and Titus offered pagan sacrifice on the site of the temple. This completed the seventieth "week."
If you disagree with this interpretation, I respect your right to have a different opinion. You might want to present your argument to me, but you cannot legitimately use analogy to one’s interpretation of Genesis one to "prove" any one interpretation of Daniel 9. That is my view.
John Oakes, PhD