Going on 10 years with my Guru and yes it has the original probes.
I bought mine mainly for those overnight pork butt smokes as I was doing 4 at a time in a 18.5" WSM. Prior to the Guru, I used a Maverick to try an monitor the temps while I tried to sleep. More than once, I lost signal due to distance from the WSM to the bedroom and the Maverick never alarmed (this was the old model, not the current ones). Fortunately I did not mess up the smoke, but knowing this had happened made it hard to get any sleep when the WSM was running all night.
Enter the Guru. Took me about 2 smokes to become confident it was reliable. I finally stopped using the Maverick to tell me the temps after a while as the Guru was rock solid and dependable to repeat the process smoke after smoke. At one time I was doing 4 butts at least once a month for the office for retirement parties and other functions. So my WSM and Guru have seen a lot of hours together.
Once I figured a process out this is how the smokes went. Plan was to have the meat hot and ready to pull at the office no later than 11AM with food service at 11:30AM. My target time usually fell between 6:30am and 9:00am depending on the meat and the stall. Never missed a food service time though. The plan was to fire the WSM with a 95% full ring of unlit topped with about 1/2 a chimney of lit (minion top light method). There would be fist sized chunks of hickory and pecan or apple mixed in with the unlit. I usually lit the WSM at around 12:30pm or 1:00pm the day before the food was to be served. Ran the Guru from the start. Top vent 100% open and one lower vent blocked except for guru port with the other 2 lower vents closed. This put the Guru in charge of the show. Button up the WSM and close the Guru vent about 90% to let the coals stabilize and the guru would lightly stoke them to a steady 225* setting. While the WSM stabilized, I trimmed and rubbed the butts. Load 2 large butts on each food grate and button up the WSM. Yes the temp would drop and the Guru would start puffing to counter the cold mass of the meat, but I still left the Guru vent mostly closed. Once it was stable at 225* again I never touched the Guru or WSM until my reload of charcoal around 11PM. Yes I know the Guru can run a lot longer than 10-12 hours, but charcoal is cheap and I like my sleep. Around 11PM, I would lift the body of the WSM with meet and top dome in place and push the remaining lit into a pile on one side of the fire ring (yes it's very heavy when fully loaded, but doing this kept the pit temp up for the 60 seconds it took me to reload the fire ring as the blanket of heated air remained trapped). Fill in the rest of the fire ring with unlit (filled about 70-80%). This gave me a modified minion relight. I found just dumping the unlit on top of the lit gave me a period of acrid white smoke as the pit stabilized again. The push to side method did not. So now I'm in bed by 11:30pm and up around 6:30am to check the pit. Usually found it in the 180* range stalled. Depending on what the temp was I knew how much time I had to shower, cook breakfast, etc... Once it started moving up again I would hit it with the spritz around 190* spraying every half hour or so until it hit at least 195* but often I ran to 200* (depending on where I was with time). This method gave me the flexibility to deal with a long stall. Pull and foil the butts and put them in a mid sized Coleman ice chest with dead air filled by a folded towel. 20 minute drive to the office and I'm ready for the hungry hoard. I held them 4 hours like this one time and they were still too hot to pull by hand (still smoking!). I've done 4 butts like this dozens of times and the Guru never let me down.
So for me if the WSM is lit, the Guru is running the show. Once you use one it's basically set and forget simple.
I do have one of the new Maverick units that I use mainly to keep track of the meat temp, but for butts I still go with the above method more by time.