If you're talking about the plain calfskin with no fancy finishes, yes it will hold up magnificently! I had one that I carried all the time and never had any problems with it. Certainly you don't want to treat it like a discount store backpack, but with a bit of care it will last for ages.
Well I don't treat any of my bags and they hold up just fine. One of my soft calf bags got caught in some rain the other day and it got a little wet. Raindrops dried and it still looks good as new. No stains or marks.
I know some gals on this forum can comment on what kinds of pretreaters they use.