They are good for lower load applications but a small dab of locking fluid/ JBWeld adds security. A light smear of a grease like copper based stuff and stainless bolts adds to a better life. You can build up a nice stock of stainless bolts/screws etc quite cheaply. I use them to replace older fixings whenever needed. Car/ garden house etc. A2 grade is ok or A4 if needed. Never on high stress safety fittings though.
Haven’t used rivnuts for a long time but if set correctly they are handy. Easier than tapping holes.
