There's a pretty tell tale 'edited at this time on this date' bit that gets added to every post.<br/><br/>I thought I'd replied but do no presently see it--answer is no to stacking but yes to chaining, which is to say you can cast on the final turn of validity and it will pick up where the other left off.<br/><br/>I ran the sims in my head when making those rituals to be certain that every 5 seasons there must necessarily be a gap, but I do not exactly have the best track record from the game so far on such issues.