Maybe we have different definitions of being high.Maybe because we do it infrequently and have not built up a tolerance, you sound like a hardened user , agreed the initial hit after injecting only lasts maybe 15 minuets or so but feeling high for us lasts quite a long time , not as long as mdma but not much less . We also have a job sleeping and get the racing heart beat for quite a few hours after the last dose so it must be doing something.
Real rush/high/peak, 15-20 mins. Maybe residual high for another 20 then sure residual stimulation for a while. For me i consider the high over after the first 20 because that is when the anxiety begins for me and the comedown/desire to redose. However you could jn theory say the drug is still having some form of effect for a while after that in that you are not technically sober. I just call all of that after effect a comedown rather than a continuation of the high
Still I would still be pretty much completely sober after an hour or two unless I'd been binging and the accumulated negative effects lasted longer