I was a heroin junkie for 21 years and for a lot of that time, if I wasn't dealing my own package I was a runner, selling for other dealers. I know when I would put wack on a package(ecp, since I'm from VA) it was usually isotol or manitol (baby laxative and sweetener). When I would get "baseballs" of tar from my weed guy in Texas, I would use milk sugar and turn it back into powder, since people in my area didn't really know what to do with tar (how much was a dose, leave some air at the tip of your barrel so you can see when you register etc...) My point in telling this preamble is to say that I speak from a long time of a lot of experience both using and dealing. It sounds to me, based on the lack of strong effects (or even getting off E), and sweet taste, y'all are getting shitty dope that's been cut all to hell with isotol/manitol. I've encountered that before and, if the dope wasn't the right kind of bitter, it usually sucked and would take a lot more to get good like I want.
I have to disagree with the fent analogs (most of the ones I've had anyway) being short acting. I was getting Butyrfentanyl HCL, 4-FIBF HCL, Acrylfentanyl and a few others for a while. The Butyrfent HCL was by far my favorite , but they all lasted about 6 hours or so per dose (I would normally rail about 5-6 large match heads for a dose, except the significantly weaker 4-FIBF, which I'd do in 3-6 thin lines, or IV about 1/3 those amounts when one of my tired ass, worn out veins would decide to party. The good fent analogs just cause such a strong urge to redose and I redosed a lot way before I needed to (I once went thru an 8 ball of BF HCL, taken in conjunction with 90mg of prescribed roxy per day and 8mg of prescribed xanny per day, in a week. And this BF was damn strong. It might have lasted longer, effects-wise, if I didn't fiend with it but, I did have a perforated ulcer with peritonitis and was hours from death without feeling much pain by the time I was convinced to go to the hospital. And I lay on the couch for about 2 weeks getting more and more seriously fucked up internally, the surgeon was surprised I was still alive.
But I'm straying from the topic and reason for why I responded to this diesel post. I think it's dope stepped on with a shit ton of baby laxative or lactose (milk sugar, available at the health food store and another common "dope stretcher". As for the short effects, I've had so-called "flash bags" many times and none of them were laced with fent analogs (maybe you're getting shitty dope laced with U47700. I hear that only lasts a bit more than an hour). In the 1990s/early-mid 2000s, dealers in my area used to lace dope with powdered morphine (not crushed pills, but real, powdered M) as a marketing technique. I uses to wish the morphine laced sauce would either stay around or they would just put good, regular H on the streets because, of course you're going to get it because it's better. Then, when the batch runs dry and everyone has regular diesel again, it takes twice as much dope (and good dope at that) even to get well. That's what I think is going on with Gorillaboy and Angelkitty's dope situations.