Back in the beginning of 2014 I was using MXE and/or K quite frequently when not hardcore. When I used these only weekly, I noticed tolerance raising noticeably, and it was generally from 200mg MXE or 0,5 to 0,8g ketamine spared 1 or 2 night max a week. I remember a specific moment using MXE 200mg a week for some weeks (1 night binge a week), on the 5th week I snorted the first 70mg with some effect, and additionnal line didnt do much aside brainfucking me a bit more. Needed to wait 2 week before effect being back to be interesting (and that was a long wait, was quite fond of the substance). So yes, I you risk tolerance from using dissociative 1 time a week.
MXE have lost it's magic for me since I began to use acid and other 5ht2a psychedelics (can't explain), now it's brainfuck, feeling tired, bad mood and pain day after. I'm missing a bit the dark emotionnal athmosphere of MXE, and other borderline psychotic stuff that I invented on this substance. But I'm able to keep the magic and a low tolerance of ketamine with using it not regularly like 1 time each 1 or 2 month (sub/near hole dose, repeated 2 or 3 time max a session).
Just to mention : used regularly (1 time a week or more), dissociative begin to take a toll on the mind/spirit, at least for me.
Never got the bladder problem atm.