Just like in any investments like the Stock Market or Forex, one should be part of something as early as possible. Yes, ICOs may make your investment twice or even up to ten times in a matter of weeks or months but I managed to see some ICOs that went down the ICO price.
What are the examples?
Titanium was $1.00 per token during their ICO. Titanium managed to surpass the $4.00 mark within two weeks of January but we all know the whole market correction during mid-January to early February. Now, they are hardly $0.10 because they were hacked with 12 million out of the 61 million total supply.
Another example is the Crypterium. It was around $1.40 per token during the ICO but now they're just below $1.00 per token.
The best way to invest is to hodl if you don't know TA but if you have the time, it's better to learn Technical Analysis so you can time properly your entries and exits depending on the market condition.