It's really gambling and luck unless you have inside info. This usually happens after a BTC rally, the top alts have pumped, then the little alts get pumped. More alt pumps that can last weeks or months then another BTC rally. The cycle just repeats 
So is it worth just buying every alt there is and holding on?
If I were you, I wouldn't unless you are okay with the possibility of losing the money, since low volume coins have higher chance of being delisted if it's not earning the exchange money. Research on coins that have development and unique features and buy those that aren't in a bubble and are in capitulation (search google images for ' market bubble psychology'). Usually I stick to high volume (top alts), then pick a few low volume alts (little alts) for high risk high rewards after BTC rallies