Question on smoking cooking time

Yes to cutting the cooking time.  Nothing comes for free, though.  Larger pieces will cook moister and more tender.  Ideally, you want to cook a full "packer cut," trimmed of most or all of its fat.

BDL

 

 I run an average of 18-20 hours on a full brisket with indirect heat at 225. If you have a more direct heat source it may take as little as 8 hours to finish your brisket. The best bet is to get yourself a Polder thermometer. This way you can track the internal temp of your product and then you will know exactly when you hit your plateau and at what temperature the conversion process began. Once your temperature starts to drop you know you have begun that process. I often find that happens at around 170 or after about 8 hours on my ceramic cooker. The longer you can extend the process where collagen is converted to gelatin the better your end product will be. In short don't rush it. A Polder thermometer is a solid inverstment and the good news is that they are not expensive. $30-40 buys a nice one.

 

Ditto what DuckFat says about getting a external probe thermometer to monitor internal meat temp.
1.5 hours, 2 hours, or 30 min per lb, there are so many variables, what kind of smoker, the outdoor ambient, etc.  1 1/2 hours is only a rule of thumb, and meat temp is what your really need to pay attention to for a nice tender piece of meat.  8lb is that just the flat or just the point?  Are you smoking to slice the brisket or you going to go for pulled/chopped brisket?  Sliced the meat needs to be tender but hold up to the cutting process, chopped you can cook the brisket a little longer.

What are you smoking the brisket on?

 

Cook it long and slow to a temp of 190 degrees

 

Yo Cabosailor,
The double chef recommendation is just that a recommendation.  It's your hard earned cash.  I only mention it because on a smoking forum that I frequent lots of guys are taking advantage of this sale.  Yeah a few have had some issues, but it is a true smoker, that can also act as a grill.  On the same forum a lot of guys also have the smokenator,  and they are happy.  Yet several have purchased the double chef. 

Good luck with your brisket...  and enjoy the smokenator...

 

If you do decide to go electric, consider what I use Masterbuilt Electric Smokehouse or MES.  There are two models 30" & 40", personally I think the 40" is the way to go, you can really load it up with food, easily smoke 16-20 racks of ribs, or just 2 racks.  I purchased the 40" for 2 reasons, 1st 3 to 5 times a year we do a big BBQ feed with family and friends, so I wanted the capacity, 2nd I like to just lay the racks of ribs on the grate whole, without having to cut or roll them (the 40" is wide enough to allow you to lay out the ribs). The BBQ smoking forum I frequent, the MES has become the electric smoker of choice.  The 40" is $299 at Sam's club, and can be more expensive at other outlets.
After reading hundreds of post about the 30" & 40" there is another reason to choose the 40", it just seems to operate better than the 30". 

My MES when it was new...