When ds was around 3.5 he started cutting down a lot. At one stage he didn't ask to nurse for 2 weeks and just said no thanks when I offered. I honestly thought he'd weaned. 2 weeks after that he asked to nurse and kept on going regularly until just after he turned 4. About a month after his 4th birthday I noticed that he was starting to skip days again. Then he started to say that there was milk there, which I knew wasn't the case because I was nursing his baby sister at the time too. He'd get a bit of milk if he nursed alongside her, but on his own he'd say there was nothing, so I knew he was starting to lose the ability to nurse effectively.
I tried everything to help him because he's get a little frustrated about it, but nothing worked and gradually he started asking less and refusing more when I offered. Then when he was around 4y3m he just stopped asking altogether and gave me these really weird looks if I offered. I didn't think then that he'd definitely weaned because of our experience the previous year, but it turned out that he really had.
He did ask to nurse again about 3 months later and I said yes, but he didn't have a clue what to do! He tried to use my nipple like a straw.
I did talk him through it that day, but he just couldn't do it at all. About a month after that, and for a couple of months thereafter, he asked to nurse, but it seemed like just knowing I'd say yes was enough because every time I said, "of course" and went to lift my shirt he'd laugh and say, "Not really."
So in short, I wouldn't think too much of it after a week of no nursing, but that is based purely on my experience of ONE weaning! lol