I would recommend always using the most current version for your modelling needs. There are some added benefits of the newer features could really make a difference in the quality and speed of your productivity. That said, if you are concerned with backwards compatibility of your files, then you could always save multiple versions of the same scene file. 3dsmax has the ability to "Save As" up to 3 versions prior to the current one you are working in. For example, if you are using 3dsmax 2020, go to "Save As", then in the Save As Type dropdown menu, you can choose .max 2019, 2018, or 2017.
3dsmax allows you also to run multiple versions of the software concurrently on the same system for studios that can't upgrade the pipeline because maybe it's tied in with a plugin or script that hasn't updated yet. So you could theoretically build your scene in an earlier version and then open it in a recent copy and save it from there as well.
