I’ve flown from BCN quite a few times over the past few months and lounge access is VERY strictly restricted to three hours prior to scheduled departure only (the staff tell me it’s an airport rule). Also, I am afraid to say I have found the check-in staff to be particularly unhelpful and they have always (with me at least) been equally as strict that you can only check-in luggage two hours before your scheduled flight, despite being open and checking in earlier flights. It’s not a great airport experience but the lounge is nice.