I use NHP 30 minute for building, and I find that it sets up a lot faster than advertised. I'd say I get a working time of 5 minutes or less, which is perfect for most of what I do. I mix it in medicine cups, which may lead to the quick setup - a lot of heat builds up. When you spread it out, like for 'glassing a wing joint, it takes much longer to setup.

I got some NHP 5 minute to throw in my box for field repairs. The first thing I noticed is that it smells terrible. The 30 minute has no odor, the 5 minute smells like crap. I have only used it for small repairs, but it has held pretty well.