First, I honestly don't know how long it takes a mock-orange shrub to establish and start flowering, but that said, I would expect (educated guess) a healthy one to starting flowering by year 3 to 4...
Below are some reasons why you might not have seen flowers by now:
Mock-oranges prefer full sun, therefore the location it's in could be a little too shady, thus slowing/hindering flower production.
- Q. Is the valley and the shrub's location within, adding too the shade?
A lot of foliage growth and no flowers is generally a sign of element(s), nutrient(s), imbalance in the soil eg High Nitrogen, low Phosphorus.
- I'd recommend mixing some Bone Meal into the soil around the base of the shrub.
Fluctuating moisture in the soil ie Prolong wetness or dryness (drought) or constantly going between the two is stressful for the shrub and can result in lack of blooms.
- Mock-oranges prefer constant moisture in a well drained soil.
Flowers appear on previous year's (one year old) growth, therefore it's best to prune immediately after flowering in the Spring, early Summer.
By pruning in the Winter you may have inadvertently removed growth that was going to flower in the Spring.
Don't prune this Winter, instead leave alone and see if you get flowers next Spring. Then if you do get flowers, prune immediately after flowering, removing the stems the flowers were on and any obvious old or dead material.
Mock-oranges can take a pretty heavy pruning, seeing as they grow fairly quickly. A yearly pruning after flowering will help keep the shrub healthy and vigorous.
One final thing to keep in mind, depending on the exact variety you have, some Mock-oranges only flower for 2 to 3 weeks maximum, therefore if the shrub isn't in an area you see regularly, you may have missed the blooms.