The regular Genesis frames are surprisingly solid, even if they start rusting you can stop the rust with an encapsulator type paint or POR-15. You can also replace pieces of the frame like the cross bar as Bruce has shown. I did that on the recent rehab 1000 and it came out pretty good, next time I do that I will measure more carefully to drill the holes that hold the new cross bar on but otherwise it was a pretty good repair. But I had been using that grill a bit before I rehabbed it, and even with a completely rusted through crossbar and rusted out bottom fasteners (bolts for the rods going from leg to leg on the bottom) the grill was still really stable. I guess I'm trying to say the frame will give you plenty of warning before it actually fails, if they even can fail.
Probably about 5 to 10 years' warning actually.
Then again, I don't stress my frames by moving the grills around a lot. My NG is parked by its gas source and really doesn't move maybe twice a year and even then only a couple feet. Maybe it's different if you're rolling it around a lot, but for what I do I just leave the grill where it is.