When I studied at the university some years ago (read: a lot of years ago), there were occasionally raids of bikes being stolen. It soon turned out to be two different kind of thieves:
- Professionals stealing quality bikes
- Amateurs needing a bike to get downtown
The first kind of thieves are not easy to stop from stealing your bike, whilst the other group is stopped by almost any kind of locks. But the first kind of thieves are able to cut through most kind of locks, even though it is locked firmly to any object.
Of course if the bike only has a simple lock, not locked to anything, it eases the job for the thieves, but my point is that if the professional thieves really want it, they are going to get it.
In my experience the best option to prevent theft is to have a somewhat decent lock, lock the bike to some object, and have an ordinary bike of medium quality. These measures have kept my bike from being stolen.
If you have an expensive bike, I would suggest never to leave it outside. When not using it, keep it inside (in garage or basement or similar), whilst still using a proper lock.
Another option if you really have to lock it outdoors, is to have it locked in a place where everyone can see it (maybe even with surveillance cameras). This will hinder the possiblity for thieves to use a lot of time or heavier tools when stealing your bike.
Lastly, the more expensive your bike is, the more you need to properly insure it, and make sure you know what demands the insurance company has related to locking your bike. Albeit I do believe your current locking scheme should be well enough for most insurance companies.