It is very rare for sidequests in this game to get closed off. It has happened to me once or twice with companion quests I was putting off, but it didn't affect my relationship with that companion too badly and if I'd really cared about them I'd have done the quest sooner. As far as I can tell there's nothing like Redcliffe or Mass Effect 2/3 where if you inadvertently do quests on the wrong order EVERYONE DIES AND IT'S ALL YOUR FAULT.