http://www.mersenne.ca/status/tf/0/0/1/0
Breaking it down I'm thinking if each 100M range has less than 2M unfactored we have the desired end result.

Similarly if each 10M range has less than 200K unfactored...

or each 1M range has less than 20K unfactored...

or each 100K range has less than 2,000 unfactored.

So I did some Excel ciphering looking at:

- how many more factors are required in each range

- how many exponents need to be TF'd at the current bit level to get there (could require several bit levels to complete)

- how many GhzDays each assignment would take.

- I stopped at the 59M range thinking current GPU TF bit levels will factor adequately (most of the time) to get below my limits of interest here.

I did this for the 10M, 1M and 100K ranges.

Then I added it all up and came up with very roughly 250M GhzDays of TF with some ranges requiring up to 10 more bit levels of TF. WOW.

In perspective, my 1,000 per day GPUs would take 250K days: 685 years.

Oh dear; that's way more than I had expected.

Note: I only considered TF.

I understand that in some (many?) cases ECM (on lower exponents) and P-1 could find factors much quicker.

In either case it looks like this will be a very far off milestone.