I am smoking right now.
and that is a very tricky question.
3 - 4 hours? what do you consider being high?
I would say you are "high" for an hour? I cant even say that cause everyone is so different that is just a very general assumption.
but you feel the effects of smoking marijuana for a long while after that maybe until you eat a meal or have a good night sleep..
or maybe after the initial buzz wears off you will not feel or show any signs of smoking marijauna..
everyone is so different...
I find eating a meal or snack brings me right back to where I started before smoking...
For me I smoke a 1 paper joint prolly a dime worth of weed.. and the initial high will have worn off like 30min to 1 hour later.. and I will just feel stoned.. hungry tired mellow etc.. my eyes won't be red tho..