You won't really need the full version; the features that will become unusable at the end of your trial period are not very important. The important functions will remain. The lack of support after 12 months is not really an issue for firewalls, so don't worry too much about that. If you would like the nearest equivalent that will continue to be supported, you could try Outpost. click here
Thanks for the tip. My main concern was that of updated protection/features; sometimes these can affect both security and stability. Based on your advice I shall stick with Kerio and not worry about the full version either until Sunbelt are better known to me or progress forces a change.