I have done far more benzedrex than I care to admit... I have never done 3inhalers in a day though, for me, I once did 2 inhalers in a day and was seeing shadow people and couldn't pee for over 24 hours and almost went to the hospital because of it. But i have read an account of someone on here doing 10 inhalers per day so I know that some people must be affected by it differently than me. All that to say, I know how appealing it can be. I will say this. I have had periods of time of doing Benzedrex daily, and I have had periods of time of doing 4-6 Yellowjackets per day (old-school ephedrine/caffeine pills they sold at gas stations back in the early/mid-2000s, they had 25mg of ephedrine and 300mg of caffeine per pill). I have also had periods of smoking/snorting meth at a gram a day, and many other stimulant phases, too. The most severe crash I have experienced was from MDMA... second most severe was from meth. Benzedrex and ephedrine both have a crash, for sure, but if you've had experience with abusing other stimulants, you might not have as bad a time as those, depending on what you have experience with. But, it also depends on how sever your addictions with other things have been. Propylhexedrine (Benzedrex) is a triple releaser, ie, it releases dopamine, serotonin, and norepinephrine, so it's definitely a strong drug. And 3 inhalers per day is a lot.
But I would just not worry about it too bad. Expect to feel down, and expect to feel cravings, and boredom, and some depression. The most important thing (for any addiction) is to find something else to focus your time and energy on. Do you have any hobbies you've been neglecting? Boredom is the worst enemy of addiction recovery.
Also, a good diet and daily exercise are important for recovery.