Okay, timeline stuff! People have a tendency to bring up the time-line that Thane mentions in the Hospital; "my favorite doctor gave me three months to live....nine months ago." (not an exact quote, but pretty close. But this is a mess up of previous established time-lines that BW themselves originally created. So, I am going to set up the time line based on the conversation Shepard has with Tali on the Citadel (if any of you know the exact quote I would forever give you chocolate covered ridges...um cookies. yeah, that's it...) where she states that it has been exactly three years since Shepard met her in the back alley of the wards on the Citadel. So working with that in-game timeline, here is a "reasonable" scenario to consider:
1) We have 3years from getting Tali in ME1 to the conversation with Tali on the Citadel in me3
2) We can immediately subtract from that timeline the following:
a) 2 years for dead/rebuilding Shepard

6 months house arrest between ME2 and me3
c) 1 month (roughly; my general assumption) from the time you start ME2 to getting Thane (assuming your not using a game editor to "get Thane early"....and for this exercise we will stick with base game setup).
3) When we first recruit Thane he says he will be fine for the next 8 -12 months (fine means active in my opinion, and after that he is too weak to fight. NOT that he will be DEAD in 8-12 months....the fact that he says "fine" and not "dead" is key.)
4) So far we have the following: 3 (years)
- 2 (years)
- 6 months
- 1 month
---------------
5 months
5) I have seen others post this before, that it is believed that ME1 took place over only a couple of months, while ME2 was longer. I admit I am not working on anything official, so if anyone has any in-game hints referring to length of time for ME1, please let me know. For now, I will use previous posters comments on this, till I can get a better verification. Based on everything we know in the two games, I would follow this is probably correct; roughly 2 months for ME1 (at least AFTER Eden Prime), and the 4 months for ME2. (don't forget, that even though the current total is at 5 months, I had already subtracted one month for time BEFORE getting Thane, in ME2).
6) So, the general timeline would appear as such:
a) First visit to the Citadel in ME1 to the time of Shepards death, roughly 2 months.

2 Years pass till Shepard is resurrected
c) 1 month pass until we get Thane
d) Thane says he will be fine for the next 8-12 months (we are currently at 2year and 3 months out of 3 years)
e) 3 months till the end of the SM
f) 6 months house arrest
g) 1 month till we finally get to speak to Thane at Huerta (this is again, my guess at how much time has passed since Shepard left Earth, went to Mars, Citadel, Palaven and back to the Citadel.
7) So, total number of months from the original "I should be fine for the next 8 -12 months" is: 10 Months
Yes, I do realize I am taking some liberty here, but working on the in-game info that Tali gives us in me3, and using other "known" timelines in game, this seems like a fair breakdown.
This clearly puts Thane still in the window of being "fine"....and anyone who has had sick family/friends or themselves knows that those terminal estimations are generally the average. Lasting a few months longer is not out of the realm of possibility (both Renmiri and myself have mentioned two such real life examples from our own personal experiences.) Because this is the timeline I would have expected them to follow (instead of making up the babble that comes out of Thane's mouth about "3 months to live, 6 months ago"), I would argue, that even without a cure/life extention, he shouldn't have been considered "waiting to die" to begin with. Further evidence that they gave him the heave-ho for character development.
I have more thoughts, but hunger is gnawing at me......must get food.