Unfortunately, yes. The ability to limit the frequency of any event happening is a pro-only feature (in which you could make it only trigger once a year).
sorry, i didnt check your account, and anyone posting threads in the main vbc forum get moved to the lite support forum.
anyway, to set the limit to once a year, expand advanced options in your Birthday event, set maximum times to 1, and limit period to 31556926 (the number of seconds in a year). Now, even if someone changes their birthday, the most often they can get that award is once a year