Dont worry about comedown, it is almost non existing, that is why lots of people tends to abuse it. Easier to sleep after than others too, no depression or headachache. Of course, if you take too much, you gonna feel like shit, but that is general rule that goes with anything. As I said, under 600 per one session should be ok.
As for tolerance - not too much after 6 months of using around 500 mg every too weeks. Of course, it is not gonna hit you so hard and last as long as first time, but still works fairy well for me.
I just repeat, dont over do it, it can be very dangerous. Take it easy and enjoy till we can