In the interest of adding information to the body of knowledge on this subject, I will share my recent experience with excessive MXE abuse:
Over approximately the last three months, I have gone through close to 15g of "high quality" MXE. My usual ROA is sublingual; occasionally, I will supplement or switch things up with oral or insufflation. From time to time, I will plug doses larger than my usual sublingual dose in search of a more strongly anesthetized state. My pattern of use is daily; most frequently I will dose once in the morning before work and two to three times after work. In general my doses have been low. In the beginning, 10mg was my "wake up" and/or booster dose. With daily use that rapidly escalated to 20mg, 30mg, 40mg, 50mg, up to the point where I can now function at about 90% at work after a 60mg sublingual dose. It is probably worth mentioning that my starter dose was often accompanied by a "functional" dose of an amphetamine.
Taking a day or two off here and there is not especially difficult, but abstinence is accompanied by slight irritability and what is probably an availability-induced compulsion to forego abstinence. In other words, I never feel like I need it but I often feel like I really want it and I am slightly annoyed if I'm not on it. I haven't noticed any detrimental mental effects of note, but if you asked my wife she'd probably tell you that my IQ dropped 20 points in the last couple of months. In the meantime, I made a bunch of new friends at work and had some creative breakthroughs that I soberly believe could lead to me finally writing that book I've always dreamed out. As far as kidney or bladder issues, I have not noticed any changes in frequency, volume, difficulty, or pain of urination. I have not experienced any "inexplicable" pain that might be tied to those organs. For what it's worth, I hydrate almost to excess (on average more than a gallon of water daily).
I should probably also mention that in general I seem to be resistant to and resilient in the face of the negative effects of drug abuse. As some examples, I quit a two year heroin habit cold turkey with no rehab, ingested close to 10g each of methylone-esque cathinones and x-(M)APBs over the course of a year with nothing to show for it but some slight anhedonia, carefully tuck myself into bed when on the verge of a dissociative-induced psychotic break, and had a mystical experience on what was probably an almost-lethal overdose of an NBOMe.
Don't take this as proof that MXE is safe. In fact, look at it as the opposite. Despite the lack of a physical addiction, the stuff lends itself well to compulsive use. If you use it excessively, you can not hide it from those who are close to you. Until there is definitive, hard scientific evidence showing otherwise, assume that using this stuff in excess will wreak havok on your kidney and bladder just like those poor little mice. Assume what science has shown to be true of them to be true of us until we are shown otherwise.
For shits and giggles, here are some of the combinations I have experimented with. Unless otherwise stated, assume low doses of each chemical. Anyone feel free to C&P the following bits into the combinations thread.
2-FMA: Dosed concurrently, reduces the 2-FMA dose threshold. Synergizes well with the pro-social aspects of amphetamines. May detract from the psychedelia of the MXE.
4-FA: Only one trial, with MXE dosed about 8 hours after the 4-FA. Apparent moderate potentiation of the MXE experience. Uncomfortable. An odd tingling/nubmness in the upper lip that returned with subsequent MXE doses 24 hours later. Will not repeat.
Ethylphenidate: Dosed concurrently, reduces the ethylphenidate dose threshold. Turned into an anxious, jittery, sweaty mess. Will not repeat.
4-AcO-DMT: Plugged a solution of something like 80mg MXE and 20mg 4-AcO-DMT (this one always hits me hard). Plunged into a nightmare world, but the setting was all wrong and 4-AcO-DMT always gives me The Fear anyway. YMMV.
4-HO-MET: Glorious combination. My ideal is a moderate dose of MXE, followed by a small dose of 4-HO-MET at first MXE alerts, followed by a large dose of each 15-30min after first 4-HO-MET alerts. The world turns into a brilliant, sparkly, colorful mess and I can't help but melt into the couch and laugh at it all. Communication is probably difficult but I've only tried it alone. Pure hedonism (if you are mentally prepared for that level of reality warping), with some insight possible if you turn inwards and embrace introspection. I usually dim the lights, sync up the headphones to a good live concert on TV, and just have a blast. Unfortunately, the comedown seems to bring an almost MDMA-esque crash along with it.
Methylone: MXE taken after the fact. Brings back the roll a bit, re-energizes, soothes the fiending, potentiates the pro-social aspects but adds a fair amount of confusion as well. Nothing spectacular. I would probably repeat it if the situation presented itself, but it's not a combo I would seek out or recommend.
DOC or βk-2C-B: Taken at the end of the trip, it potentially turns that long, drawn-out comedown into an otherworldly adventure, similar to but not as fantastical as the 4-HO-MET combination. Likely to repeat, if only because what else am I going to do on a 10+ hour comedown?
5-APB and 6-APB: Only tried this combo once and it was nirvana. Started the evening off with a combination of something like 90mg 6-APB and 75mg 5-APB. At around four hours I added about 20mg of MXE to test the waters. Liking what I saw, I promptly added another 60-80mg of MXE along with 10-20mg of 4-HO-MET. Inspired me to write an as-yet unwritten post. This was quite probably the peak hedonistic experience of my life. Only time will tell, but it may prove to be a ++++. THIS IS NOT FOR THE FAINT OF HEART. I have heard of others having VERY BAD REACTIONS when combining MXE with APBs. Make sure you know your mind and know your body before attempting anything like this combination.
5-MeO-MiPT: A threshold dose of MXE, ~4mg of Moxy, a couple beers, and a couple bowls, and I am ready to party all night. Not much else to it, but damn fun.
If I think of any others I might come back and add to this, but I'm trying to get my head straight at the moment so it could be a while. Proceed with caution fellow psychonauts.
Is the tolerance self-protection lol? Maybe it is better this way, but it is also super freakin annoying 
