Rocky got it by the time he was 3 or 4 months but would still have accident if I didn't catch his signals or didn't take him out often enough. I never trained him on pads and have taken him outside since he was 8 weeks old, rain, snow or shine - he loves rain and snow btw. He's now 8 months old and I still take him out very regularly when home in the evenings and on weekends, about once every hour or two. He's crated while I'm at work (I just bought him the great-dane size crate so he's got a little more room - he hasn't soiled his crate since he was very small) and I go home at lunch to let him out. He sleeps all through the night and is free to roam but he stays on my bed. I agree about the bell training. I certainly am not brave enough to say he's beyond having accidents but he's good about ringing the bell when he wants to go out. If I miss it, he'll pace back and forth between me and the door.
A funny thing about the bell is that he'll ring it just because he wants to go out and play. He'll always give a performance though by going potty, even if it's just a dribble as if it's to justify the trip outside. Then he wants to run and play. He's got me trained alright...