With Backup Exec, I always did full Exchange backups. Every day. Yeah, I know
Each backup was a B2D, and the files were in their own directory. Each full backup was 300G or less and fit onto a single tape fine.
With Veeam, as I said, I have a single job that does Fulls once a week, and Incr the rest of the days, all to a single directory. So far, that dir only has 276G in it. It will fit just fine onto one tape. However, in a couple of weeks, once I have a few fulls and incr files, it might grow more than the 780G.
So, I can either have less B2D retention, or start spanning tapes for my "weekly" full tapes.