I very rarely have to touch my printed corners. They are printed with PETG that I print at 260C. I don't usually print with ABS just PLA and PETG so my build plate very rarely gets above 75C so I don't have any melting or loosening of my corner mounts.
They hold the glass steady yet are just loose enough to lift the glass out without messing with the thumbscrews.

I've only tried PETG by Makergeeks and I like how it prints albeit at a higher temp the ESUN PETG.
I print MakerGeeks PETG at 255C and Esun PETG at 235C they both have worked great for me.
It looks like Makergeeks filaments print at a higher temp the some other filaments.