I do not mind leaving my coins on freebitco, and as you said, the interest can give us additional income, although it will depend on the amount we deposit. But on the other side, I will not let myself to store my coins on that site because the risk will be too big. But for freebitco, I trust the site and I believe that the site will not run away. Besides that, freebitco has good reputation among the other site.
No matter how trustworthy they are, I will never keep my coins in freebitco, or in any other sites. Trust doesn't matter much in the Bitcoin sector. Back in 2012-13, Mt Gox was regarded as the most trustworthy cryptocurrency exchange. But what happened after that? You never know when these sites will go down, irrespective of their good reputation and trustworthiness.
It is okay if you will not keep your coins in freebitco or the other sites. That will have our consideration to prevent any scam that can happen in the future, and I believe you are doing the best thing for yourself. Mt. Gox is the biggest lesson for us to always careful to decide. But at least, I still want to get additional income from freebitco, but I will withdraw all of the funds in that site when I can see my profit become bigger.