Unless you have control over when they are made and can download them as they are made I would not rely on that. I have a VPS and the server died once, when the server came back online the database backup they restored was three days older than when the server failed as was everything else. e.g. log files were missing 3 days and as another example files that been uploaded were missing. I had my own backups so it was no big deal.
Another hard lesson to avoid is the importance of having revisions. e.g. you accidentally set a forum to prune posts and never realize it for a lengthy period of time. If your oldest backup is after it was pruned you are toast.
The script I linked to above by default will make a daily backup for say Mon to Sat. It will delete the the backup from last Monday when a new week starts. On Sun. it will create a weekly backup in different folder, those are rotated out after 5 weeks. It also creates monthly backup, by default those are rotated out every 6 months but I keep them all.
In other words i have backup for each of the last 7 days, I have backup for each of the last 5 Sundays and I have a backup for the first of each month going back years.
That is jut the tip of the iceberg for that script. It does incremental backups, will encrypt the backup, email backups and i thin it will even upload them to offsite service etc. I have my FTP client scheduled to download them.