They're rock solid stable, so just observe common procedures: Store in sealed vial, out of direct sun, at vaguely room temperature. Storage as the powder is recommended, but it will keep indefinitely in solution as well (provided that you ensure that nothing starts growing in the solution).
This is true of phenethylamines and amphetamines in general (tryptamines and cathinones/MDPV, as well as coke and heroin must be stored dry, not in solution; LSD should be stored in darkness and in a cool environment - room temp is OK, though some people put it in freezer, and it is stable in solution as well as dry (per Shulgin)). Most everything is stable if stored in sealed container, dry, at room temperature, and the majority of drugs are stable in solution as well; impurities generally reduce stability (or may present the appearance of instability, due to the impurity degrading).
Seiko, I don't remember Shulgin addressing the question of stability directly in PiHKAL - but I may just not remember. I know he talked about it for LSD in TiHKAL.
2C-I is more like 2C-B. They're quite similar, actually, with 2C-I being more visual, and some get more physical sideffects with it. If I was randomly given 1 of 2 2C-X's, I would have the most trouble distinguishing between 2C-I and 2C-B. I would say 2C-B is more "warm" than 2C-I, 2C-I is more "crisp", for what those adjectives are worth. Both are generally considered pretty shallow, as far as psychedelics go.
2C-E I would liken more to LSD than 2C-B, in all honesty (of course with a different timeline, and differing sideffect profile - more people get stomach discomfort from 2C-E than LSD (or 2C-B, for that matter), though not all do). 2C-E can be every bit as deep as acid, and is quite visual as well. 2C-E is not a psychedelic to be taken casually.
PiHKAL has some great descriptions of the effects of the phenethylamines, and as seiko said, you should definitely give it a read. It's a good read in general. It seems to me that he chose not to contrast them against each-other. I have to assume he intentionally avoided doing this, which I can understand his reasons for.
thanks.
