I would recommend you withdraw your coins as soon as you are done exchanging as my withdrawal experience with them has been nothing short of terrible. They offer some lesser known coins which is why I used them but my withdraw took over 2 weeks to process. Support is essentially non-existent and I would try to avoid them unless you have no other choice (eitherdelta and coinexchange often offer similar coins).
Of course this is just my experience with HitBTC and yours may be different. I don't think they are scammers as I eventually got my withdrawal but they are definitely incompetent at solving even trivial issues.