We have a similar plan to what you propose, as our standard for about 60 servers, varying in size from 1/2 GB to 128 GB.

Sun 7:00 pm - Full backup WITH INIT

Mon-Sat 7 pm - Diff backup (append) to same backup device file

Midnite - 6:59, and 8:00 pm - 11:59, Sun - Sat : tran log backup every 15 mins. These are to a different backup device file (i.e, "DBname_Log.bak"), which gets an INIT every eve with either the Diff or the Full.

We can restore back to point-in-time TODAY, or 7 pm THIS WEEK. This has happened in practice a few times in the last two years.

If we need to go previous to Sun. Eve, we will pull needed files from a disk image on tape.

I think the INIT is what you're referring to by Truncate - it clears the old backup file on Sunday night, and the old Log backup file every evening.

For two of the larger applications we use LiteSpeed backup to save drive space and time, but otherwise the same strategy.