1.5g shrooms 6h??? No way, I highly doubt there is any kind of shroom with such long effect, also for me effects are 1.5/2h with less than 1g.The ones I took seem to be pretty weak, the peak was over in like 1.5h, afaik it's supposed to last 6h?
I don't know if 5g will give you 6h but I doubt it too. For 6h you have to go with half or full dose of lsd.