It is strongly recommended that unless there is a need to maintain a model file in an old version (e.g., your client only has that version), you should upgrade your model to the latest version. This is because the latest version will have the greatest number of features, and will also have addressed any significant bugs that were identified in previous versions.
The latest release of GoldSim can generally read in files created in the previous two or three releases of GoldSim (and often can read files created in much older releases). For example, GoldSim 12.0 (whose latest update was released in February 2017) can read in files produced by versions as far back as 9.60 (first released in March 2007).
Of course, when reading in a very old file, although GoldSim may be able to read it, the file itself may not be able to run without first making some changes (since some of the features may have been changed too extensively). When changes are made that can affect the ability to run a model, this will always be specifically noted in the Summary Document produced with each new release. For example, several changes were made between 10.5 and 11 that could possibly impact conversion between those releases in rare cases. These are described in detail in the GoldSim 11 Summary Document. Similarly, a smaller number of changes were made between 11 and 11.1 that could possibly impact conversion between those releases, and these are described in detail in the GoldSim 11.1 Summary Document. Most of the changes between 11.1 and 12.0 are cosmetic, and any conversion issues are discussed in the GoldSim 12 Summary Document.
If you have any questions or need any assistance with the process of converting a file, contact us via the GoldSim Support Desk.