That being said, a little more info would also be useful. For starters, is it a point or a flat? Next, what type of smoker are you using? Is it capable of higher temps? Do you want to do low and slow or hot and fast?
For me, a hot and fast (300˚) smoke of a piece of brisket that size takes about 4 hours to reach 195˚. Others do it at 225˚, some go even lower. Some take it to 165˚ and wrap it, others take it to 165˚ and then steam it. I believe the steam or wrap method is more beneficial for a flat than a point, as the point usually has enough marbling to handle a straight smoke.
Once you figure out your plan of attack, please come back and post your methods and results. This forum is a 2 way street. By posting your cook and any successes or failures, you're adding to the knowledge base so others who come after you might benefit from your experience, then in turn, share theirs.
You need to smoke/ cook to internal temps, not necessarily time as each cut of meat will do it's own thing as far as time goes. There are no absolutes and all your questions have been answered in past posts. What more are you looking for???
You can go the hot and fast route or the low and slow route, Both work. It's just a matter of personal preference. Best of luck with whichever you choose. It's all good.
Speaking for myself only...as to why we want to know what you're smoking on...with smokers, it's what style...offset? Kettle? Kamado? Electric? If we were into cars, we'd be asking the same questions about what you have under the hood even if you asked for help with the tires...it's just what we like! Many folks here are fanatics, and will go to great lengths to tell you what they learned the hard way...but as mdboatbum said, it helps to know where you're coming from...pro chef, or (like me), guy who can barely light a match...you'll get great answers either way, but the most useful answers need to know where to start.
If you are planning on smoking one of those corned beef briskets that are pre-brined and ready to boil, you might want to consider soaking it a few times and changing the water out to remove the brine. I soaked mine for 4 hours and thought it was still quite salty when I tried one of those. Also, in retrospect, I would have probably had better results with a temp. probe.