Successes Needed for Extended Rolls

So I was trying to figure out the number of successes required to do certain jobs in the WoD/GMC as well as the length of time for each roll and I came up with the idea of trying to use some real life estimates to generate those numbers. To do this I start by figuring out the number of rolls that a 'professional' would need on average to complete the job as well as the average length of the job.
As an easy example, if something takes an average of 4 rolls and an average of 4 days then each roll takes one day.
Now the problem that comes is this; just what is the roll for this theoretical 'professional NPC' that is used to generate these baselines? Does our baseline NPC have 5 dice (assuming a 2 and a 3 in attributes and skills)? 6 dice because of a specialty? 7 dice because their base stats should total to 6 plus a specialty? 9 because we can assume that the baseline professional has access to equipment giving them a +3 bonus? And what about things like having 9again from Professional Training2? Should the roll be considered a rote action since professionals usually do highly similar activities over and over again?
I've already got some ideas for these (and I'll throw them out later) but I'm curious about what other people think are good rolls for a theoretical baseline professional.

In general I tend to give nameless NPCs 68 dice in whatever their base competency is, 6 for the base level professional up to 8 being the top person in the area at a thing with out being famous for it. That is without equipment.
NWoD dice, both GMC and 1st, are worth 1/3 a success on a normal roll with 10 again. so if you figure nine dice that would be 3 succs a roll on average. So if you wanted it to be something that would take the average pro 4 rolls than go with a threshold of 12.
On the other dice cases you mentioned 9 again does not add much changing the expected successes per die to roughly .38 per die.
Rote in the other hand changes the expected successes quite a bit to being 5/9 successes per die, meaning the average roll of a nine dice pool would yield 5 succs so if you wanted it to take 4 rolls you would need to increase the success threshold to 20.

@ThatGuyThere Actually, the average number of successes for someone rolling 9 dice 4 times is around 15 because of exploding contributing more than you think (http://anydice.com/program/bd0a. Thanks to Misadventure for pointing me to the site).
And while things like 9again may not contribute too much to a roll by the time all is said and done they contribute a great deal more than you might think. After all, someone with 6 points in combined skill and attribute will roll 54 dice (assuming a +3 equipment bonus) so at the end of the day an extra 10% here and an extra 5% there adds up to a lot of successes.
But the real point of this thread wasn't to quibble about how much ability A helps or how many extra successes ability B will generate. It's just to figure out what the theoretical pools (and any roll modifiers) should be.
At present I think I'm more or less in line with your estimates. I'm actually ranging from 48 dice with the 4 dice being the skill level of your average entry level professional. These are the guys on the construction crew that do the real simple jobs. You have them handle the framing and drywall when the job is easy but in the spots where those tasks get tricky you have someone who's been doing the job for a couple of years now come in and handle it. 6 dice are your true 'average professionals' who are fully trained. They've been doing the job and 95% of the time if you want the job done you call these guys in. 8 dice are the true experts. Not necessarily worldleaders in their field but they are they guys who get called in to do jobs that even your normal professional would consider to be difficult.
Then what I did was I figured out the average number of successes for 1 to 6 rolls as an extended action using a rote action for 7 dice, 9 dice, and 11 dice. I assume that the vast number of extended roll activities your average professional does are rote actions. Sure, the tailor needs to modify the pattern for the custom fit jacket they are making and everyone's body if a slightly different shape but they've done so many jacket alterations, plus they have the time to sit down and work out any tricky areas that might exist, that it is still a rote action for them.
Then I figured out how many rolls you would expect someone normally doing that job to take. If your 'average professional' would take 12 rolls I used the average number of successes for 7 dice because the average person doing that job is a bit less skilled. If it was 34 rolls I used the average successes for 9 dice and if it was 56 rolls I used the average number of successes for 11 dice.
This seemed to work really well because the guys with the 4 die pool could nearly always accomplish the '2 roll' task (99.96% of the time). It might take them twice as long to get it done (because they had to make four rolls) but they would nearly always be able to, much like you would expect in real life. Meanwhile the odds of that person pulling off a '3 roll' tasks is about 50/50 (meaning that they were around 75% likely to succeed if they took 3 times as long as the 'fully trained' professional. Meanwhile the 'fully trained' pro with their 9 die pool would nearly always accomplish a '4 roll' task (99.21% of the time) but dropped to around 50% odds of succeeded at a '5 roll' task.