One of the cardinal technical rules of Elliott Wave Theory is that wave three cannot be the shortest wave. If the wave we find in the third wave position is the shortest, then that tells us the pattern isn't what we think it is. The Philadelphia Bank Index (BKX) is currently providing us with an excellent tell in this regard.
The hourly chart of BKX below. The nice thing with the BKX pattern is it's telling us "either the rally ends here, or it's got a lot farther to run." There probably isn't much in-between.
SPX hourly below: