Coke tolerance goes up like a rocket. You may have very cut cocaine, you could wash it with acetone to get most of the cuts out, there's a lot of threads on that, if you wanna find out roughly how pure it is...
Basically, coke tolerance goes up fast if you binge... With pure >95% cocaine a dose for a non tolerant individual would be 10-30mg. Once tolerance comes into effect, it never fully goes away. If you abstain for a a while then use again, the first dose will be similar in effects to a non-tolerant person, but once you've had tolerance, it will build up more quickly the more you use. Cocaine tolerance goes up very quickly due to it's short half life.
If you want to maintain the tolerance you have and prevent it from going up like a rocket, you need to control your usage and limit yourself, also, if you are going to continue to use, only snort the good stuff, do an acetone wash and get most of the contaminants out so you have a fairly accurate estimate of what you're really putting up your nose. Also, I recommend getting a mg scale. They're like $20 for a cheap one but it'll get the job done. The cuts in coke will contribute to the comedown. Pure cocaine has almost no comedown with non extreme dosages.
Bottom line, Know what dosage you're actually putting up your nose, control the dosage, never iv the shit period.
Coke isn't my DOC and I very very very rarely use it, so YMMV.
Stay safe and sane.