my 13 week old retriever now holds herself for  3 hours in the am and 3 hours in the pm. at night she can go 6 hours without a wee.The problem is in the evenings. I can take her out for a wee then about 30 mins later she will,without any warning , just squat down and pee! It's so frustrating and she doesn't seem to bother about doing it which i cant understand cos she must know she should hold it till she gets taken out because she does this when i am not there or she is confined to the kitchen.She is fine with pooh's.if she wants to go she will whimper and run to the door.It's the peeing thats the problem.I don't have any paper down as i followed advice off this site so she will just pee anywhere in the living room without warning.
Can anyone give me some advice?
Thanks

First question is how are you clearing up the accidents? And how do you react when she does it?

Iv got a 16 week old boxer bitch, I had the same kind of problems you are encountering.  First thing in a morning she would have her food then go in the garden to do her wee and a poo,  all day long she would go in the garden when she needed to go.  Then in the evening she would wee in the front room or kitchen. My theory was that that was the time we were spending less time watching her and paying attention to her and she could smell where she had been b4.  I bought some stuff that cleans up and masks dog urine from the pet shop and started to take her to the garden every half an hour in the evening during commercial breaks usually.  It seems to have worked because she now goes in the kitchen and whines to go out instead of just doing it.  Shes been ok now for 2 weeks. good luck

If she goes 30 mins after you come in then you will have to take her out 30 mins later. 

Rox

when you bring her in on a night allow time to take he out approximtly half an hour after shes in and see if she is going then..we had a similar problem with one of our dogs and we had to keep nipping her out and praising her wen she weed outside and eventually she stopped..if she is going outside for her poohs then she knows the difference between indoors and outdoors and it is probably just a weakness rather then a naughty act. good luck!!

At 13 weeks she's still very much a baby, and I would think she's just forgetting herself.  Also, many pups pee 'best' when they're relaxed - often when they come back into the house where it's warm and comfy and there are fewer distractions. 

At this time of year PERSONALLY I would have paper down just in case - at least if she feels the need to have a pee and you aren't aware, there's somwhere she can go without getting in too much bother.  She'll grow out of it soon, don't worry.