I think the tolerance thing is fairly misunderstood.
First off, tolerance doesn't mean that if you eat a substance 2 days in a row that it won't "work" on the second day. I doesn't even necessarily mean that you won't "trip as hard" on successive days. The latter is true in a general sense, but it usually takes quite a few successive redoses before there is a highly noticeable diminishment of psychoactive effects.
What is happening is that after your serotonin receptors are flooded with exogenous tryptamines they experience down regulation, meaning that they compensate for the flood of neurotransmitters by pulling in some of the receptors so that there are less available receptors to take up the onslaught of exogenous molecules the next time you dose. So if you dose again before they have had time to recover and up regulate, you'll experience further down regulation, and again, and again, and so on and so forth. Successive down regulation can make it difficult or impossible for the cells to up regulate receptor density back to previous levels. Beyond the diminished psychedelic effect, this means that as you go about your day to day, your nervous system will not be able to utilize your normal endogenous stores of serotonin and other tryptamines as efficiently, and as we are all aware, this is associated with lowered mood and depressive symptoms.
There is a study showing that ayahuasca up regulates platelet serotonin levels, but this doesn't necessarily mean that up regulation is taking place in the nervous system, or anywhere outside blood and plasma. Theoretically, the MAO inhibition effect of harmalas would lead to increased neurotransmitter levels at the synapse and downregulation of receptor density, as happens with reuptake inhibitors. Further research will be required to understand the mechanism by which ayahuasca has this up regulation effect, and whether any upregulation takes place in other areas within the organism.
From a neurological perspective tripping less frequently is both safer and will provide more profound effects when you do trip. Not to mention the importance of taking time to integrate each experience, ground back into ordinary consciousness, and explore and apply the lessons learned within the psychedelic state. Perhaps consider trying bigger doses less frequently if you are feeling compelled to return too soon.
