The only thing you'll want to look out for is if you include crushed garlic in your dressing... for the same reason keeping homemade garlic oil is not a great idea.
But a vinaigrette made from oil, vinegar, mustard, sugar, salt, pepper, and a few herbs should keep at least a month plus in the 'fridge (mine have anyways!).
All of it sounds good but you usually lose alot of the freshness of a homemade dressing after a few days.My sherry shallot vinaigrette always loses it punch after about 2 days.It just becomes kinda flat.But then again this one may be better after a few days.You will figure out if its better or not when you finally try it.
You should be fine for at least 3 weeks as long as you don't have garlic, which you didn't include in your ingredients list. Garlic is friends with botulism, so stay away from storing your dressings for any length of time that include fresh garlic.