There are many forms of fungi (mold, various rot) that can feed on wet wood. There are not many forms of fungi that can feed on cured adhesive, which also functions to prevent the wood that is there from getting wet. Thus, I'd expect engineered/laminated timber to be better at repelling rot than standard untreated timber. Done well, it could last longer than steel.

If anyone on HN has never hoisted an LVL beam (or even glulam), I would highly recommend it.

Suffice to say they're 'quite a bit' heavier than wood.

That weight is the adhesive and/or compression. So we're very much not talking about 'tree wood' at this point.

It depends on how the material is designed. Some materials like commonly available particle board, can't get wet at all. They swell up and crumble. On the other hand there are grades of plywood that are rated for wet applications.