Database Backups of 2GB+
Some important factors to consider for backup are:


how annoyed the forum users would be if X days of activity disappeared
the probability of that happening
how long will it take to recover the data if it's backed up
how much does backup interrupt the normal operation of the site



As for, "Am I making sure my data is protected enough ...?", I'll ask a question back. What Recovery Point Objective (RPO) and Recovery Time Objective (RTO) are you aiming for?

Your current backup schedule has a recovery point of


for the current month, to the nearest weekly backup
for the last three months, to the nearest 1/2 monthly backup
for the "life-time of the site", to the nearest monthly backup


I'll suggest that you add daily backups to your rotation. If space is a concern, look into differential backups that only backup the data created that day. If space is a concern and RTO is not of paramount importance, you can reduce the size of backup files by compressing them. Backups of a DB containing primarily text might compress well.

By the way, if your forum keeps growing at an average of 200 MB/day (and growth is not accelerating), that's 6 GB/month. If you keep doing full backups on the schedule you outlined and backups are more-or-less the same size as the forum DB and they aren't compressed, by the end of the year you will have:


January monthly backup, 2 GB
February monthly backup, 8 GB
March monthly backup, 14 GB
April monthly backup, 20 GB
...
September monthly backup, 50 GB

September 1/2 monthly backup, 53 GB

October monthly backup, 56 GB

October 1/2 monthly backup, 59 GB

November monthly backup, 62 GB

November 1/2 monthly backup, 65 GB

December monthly backup, 68 GB

Week 1 backup, 69.5 GB
Week 2 (December 1/2 monthly) backup, 71 GB
Week 3 backup, 72.5 GB
Week 4 backup, 74 GB



approximately 1 TB of stored backups. And backups will be taking 20-40 times longer than they are now. An interesting followup question would be, "Are you doing cold or hot backups?"