I got bored and made a size 16 map, put a huge hollow tower (as high as it could go). Inside it is an escalator which spirals up around the walls eventually to the top. Each wall had 9 escalator pieces, and there were obviously 4 walls. Each escalator piece took 40 seconds from beginning to end. Based on this I calculated that it would take roughly 1,440 seconds, or 24 minutes for the escalator from beginning to end. It took quite a long time to build, even with copy/pasting.