How Safe are Your Jack Stands???

I don't have expensive ones, but they are multiple times better than the sheetmetal stands and ramps I had as a young idiot.
I'll add that the only time mine were anywhere near maxed out in height was during resto and the car was only a shell. I also wouldn't have them on either side of the diff, I like to get them about as wide as the framerails. I will be going to look at the weld quality though. I might also weld some additional footing on them, but so far I've also only had concrete driveways, no tarmac.