And Joshua set up twelve stones in the midst of the Jordan, in the place where the feet of the priests bearing the ark of the covenant had stood; and they are there to this day.
Joshua 4:9

The active memorials ("Do this as a memorial...") commanded in Torah were given to remind us and future generations of what God has done for us. Physical memorials like the one Joshua set up eventually fall (the stones must have been very large to withstand the spring floods year after year, but they aren't there now), but the same isn't true of active memorials. it isn't possible to "fulfill" an active memorial, such as Passover and Sukkot, so that it is no longer necessary, unless we no longer need to remember God's love and guidance.