You can certainly upgrade to a version that is "outside" of your "support" period. The updater is not smart enough to know better. (Actually many people post here when this happens). I think you will just have to manually look at the updates and find the last one that was released during your support period. As long as you install a version that was released during your paid support period, you should be fine.
If you happen to install a version that was released after your support period ended, your software will switch to "evaluation" or "demo" mode and you have 15 days to correct it (which is to be expected since you are using an unlicensed version - just like someone who is trying BI out for the first time). Don't worry, it's not the end of the world if this happens. You can either downgrade to a version that was released in your support period (by simply installing the older version through the update process), or you can pay another annual fee and restart your support period which will validate that version and allow you to install the latest versions as well.
If your version is old enough that it doesn't support "substreams" like the new versions do, I highly recommend that you pay the annual support fee and update to the newer versions.