We had a pretzel at BGW the other day and that thing had to of been in the warmer all day....it was hard as concrete.
Honestly.....that's the sign of a great soft pretzel. In a warmer like that, good soft pretzels should only last about 2-3 hours (tops) because they are still holding moisture. The outside should be cooked (put in boiling water) in some type of crisping agent (caustic flakes boiled in water is the best), and when baked (put in the oven) it should be done till just barely golden brown. If you cooked the pretzel right, after baking there will still be moisture in the dough with makes it soft. The downside is there isn't a great amount of shelf life. It why many places go for a bread based dough, because when cooked (baking soda) its not cooked in a crisping agent, and it's also baked much longer (baking in moisture) to have a longer shelf life.
To quote my credibility on this topic:
https://books.google.com/books?id=7...q=mumma's pretzel bakery lancaster pa&f=false
Take a look at the caption, the name of the guy behind the counter, and deduce from my username