Good question, especially since many are sometimes less than regular with their practice.
Now, from my own experiences and many times through the material over the last year. I would say that there is some loss of benefit, but not a loss of progress.
Remember how Master Lin describes the SFQ practice and experience and says that you a student often experiences a powerfull sensation of qi when first starting. Then after the channels start to open they lose the feeling of qi and are often disheartened and their practice falls off. He also says that this is the best time to experience the benefits, since the channels are more open the qi can move more freely than before.
Master Lin also talks about the sitting meditations as opening the channels and the active meditations of building capacity / the flow (these are my words/understanding of his words ... just about a week ago, maybe I should check the exact wording). I have never heard him mention that the channels would close, nor that the qi reserves or flow would lessen. So this is my conjecture, based on my NOT always regular practice. I would say that your channels will stay open. You retain your progress. You retain your capacity. However, you do experience a reduction in the amount of qi moving (storage/reserves) in your universe.
The nice thing about this is that you have the capacity and can fill it quickly. You don't have to rebuild your capacity.
-----
Just some more rambling. In the physical side of yourself. You can build muscular strength and then stop training and then loose the newly gained ability. However, if you try and regain this strength level within 6 months of stopping, you can rebuild it at 3 times the rate that you originally built it. I just add this as a parallel. I would not say it is an exact parallel, and I would expect similarity but not exact duplications in the mental, spiritual, and physical self.
-----------
As a final close, my intellectual buttock side of my wants to answer 10%. 
Morningstar, your benefits will be phenominal. Don't forget you can get benefit from the active exercise, even if you only do them mentally.
------------
Even more rambling. Sometimes I invite Master Lin to merge his energy with my other times I just invite him to do the healings I want. They are both powerful and different experiences. Don't hesitate to invite your Master's energy, it will be there to help you, as you need it. You need but ask.
You are perfection.
Iam2 
