High-quality software is only one part of what we are selling. Equally important is ongoing support.
We only have one class of support. If you contract for support (by paying a yearly fee), you get everything we produce: bug fixes, enhancements, etc. We don't charge separately for new language features and major enhancements. We are also happy to give advice on making changes and to give opinions on language issues, and we'll accept requests for enhancements if they have general utility.
As the standards for C++ and C evolve, we update our products to match them, and customers who remain on support get versions of the front end that conform to the new standards (at no cost beyond the normal support fee).
We typically send out a complete release of the C++ front end every 4-6 months. In between, we send out source patches for high-priority problems. If you run into problems that require immediate attention, we will try to get a fix to you within a few days. For less pressing problems, we will usually fix the problem in the next release.
Within reason, we are always willing to provide patches for bugs in older versions of our front ends. We understand that our customers will have to maintain shipped products for years and that switching to a newer version of our front end may not be practical at the time a bug turns up.