Altcoins can be very profitable if you get to risk your funds on the right coins but nonetheless altcoins unlike bitcoin isn't an investment you should hold for too long due to its pump and dump nature. 50x returns if achieved is a significant profit to be made though but hanging on altcoins in anticipation towards the bull run peak before selling or taking profit isn't anything I'll want to do because most altcoins may not even wait till the bull run peak before dumping and that's why it will more better to take your profit provided it has made some significant highs than waiting till your projected timeframe.
Spreading your sell offers upwards as far as you imagine price might go, and actually I prefer way higher than that as historically for me they have often wildly exceeded my imaginings, helps make sure you don't miss the peak, just as spreading your buy offers all the way down, or at least significantly down, helps make sure you don't miss the buying opportunity presented by dumps / tanking of the price.
-MarkM-