I'm in a similar situation, eat very low carb and taking between 1 - 3 units of levemir a day and 0 novarapid. At first I thought, hey, I'm cured! but like you, if I eat carbs without insulin my sugar levels sky rocket to.
I've been type 1 for about 18 months now and didn't always take this low amount of insulin until I started exercising and eat low carbs, so I'm not sure if I could call it a honeymoon period or if its a result of lifestyle changes.
When my insulin requirements dropped so little, I searched a lot on the Internet to see if anyone else was like this and there are plenty of type 1's who don't take any insulin at all. If you google raw food diet you'll find some people who only eat raw food and don't need insulin. I'm pretty sure this is because they are eating tiny amounts of carbs and protein and type 1 is classified as 80% or more of your pancreas beta cells not working. So if you are eating a low amount of carbs and protein and still have 20% of your beta cells producing insulin, you would in effect not need insulin because your insulin requirements are handled by your natural production of insulin.
I have also read that low levels of insulin are healthy, but I don't know if too low could be a problem and I can't find any info on this. If you're taking only 5 units of levemir a day and your pancreas is producing some insulin throughout the day, is it enough to keep your hormones balanced? From what I've read insulin is only needed to maintain sugar levels, but a lack of it will also cause incredible weight loss. So I guess the only problem taking small amounts of insulin because you're eating low carbs is that it would be nearly impossible to gain weight and incredibly easy to lose it.
For the last few months I've experimented with lowering my insulin more and more, until the point of taking only 1 unit of levemir a day. In just under 6 months I've lost 40lbs, going from 188lbs to 148lbs by eating a high fat, very low carb, medium protein diet. As I've lost the weight my insulin requirements have dropped from over 20 units a day but I still don't think my diagnoses was incorrect, we just require small amounts of insulin because we produce some insulin, require small amounts from our diet choices and are sensitive to the insulin we do inject.