Although you, the concert organiser, may be excited at the prospect of a recital lasting 90 minutes-or-so, ask yourself if the audience will share that enthusiasm. After all, the last thing you want to do is put-off people from attending in future because "the previous recital there was too long". An hour is probably the maximum time for a 'straight-through' concert, i.e. with no break. For longer recitals, perhaps an interval with refreshments is an option? If dealing with tea cups and wine glasses, etc. is out of the question, a five-minute 'stretch your legs' break may be in order. Such a break won't add substantially to the event's duration but, after it, people will sit down with renewed comfort and anticipation.