This is an excellent point.
In terms of purity, it sounds like your basing you "70% salts" (I'm guessing you mean actual salt, not random RC's labeled "salt") on your experience- I know first hand, my first few months of MDMA use, 60 mgs had me going all night- now, even with my use only every 90 days or so, in order to equal that experience, I'm typically dosing 200-300mgs over the course of the night. Point being, considering you use frequently, it's extremely likely it's you and not the strength of what you have.
It sounds like you want to convince yourself circumstances make it OK to re-roll in this case, I think we have all been there at one point. I'd really advise you to try to make a habit out of waiting it out, and making those "exceptions to the rules" span a matter of a week or two, rather than a matter of just a few days. This will assure you will be healthy, and able to continue enjoying MDMA in the future.