What's a good length for a promo video. Would you say 1 minute is too long?
I think it really depends on the trailer. I've seen cinematic-style trailers go up to a little over 2-minutes and keep my full attention, and I've been bored by 30-second trailers that just quote reviews and offer nothing interesting visually and/or don't seem to follow any script.
(I would say that as between a slightly longer trailer and keeping your captions up long enough to be read, err on the side of making a slightly longer trailer.)