I can’t say I’ve ever had mould on my wood furniture. I have had a metal base which was cheaply made and bent after very little use, so I’m a bit wary of metal frames. It was when I was a teenager and money was pretty tight, Mum managed to buy my sister and I new bed frames to replace the tatty second hand wood ones we’d had since we first moved into full beds, and within a year they had both broken and we ended up sleeping on matresses on the floor for a few years.