Almost any steam iron is practically BIFL if you use only distilled water in it.

If you apply starch/sizing to your clothes, keep an eye on potential buildups on the hot plate, gently scrub them off with a generic magic eraser and rinse off the residue.

Don't let it fall to the floor.

That's about it.

For ironing boards, buy a quality pad. Don't let wet or damp items lay on the board repeatedly. When you're done ironing, if the pad feels moist, take it off to dry separately. These steps will keep the board from rusting.

Lightly oil the track the legs slide in.

These are simple devices that last a long time if a little care is taken with them.

Rowenta and T-FAL are the BIFL iron brands. Use and type of clothing don't matter when buying. Some models come with a sacrificial anode so you can freely use tap water, otherwise best practice is distilled water use.

Boards are harder as there is no consensus and this varies more on YOU than us as some like small ones, some large as this is an ergonomics question vice lifespan as there is no lifespan winner. A piece of wood wrapped in an old wool blanket will do in practice.

I second u/Muncie4 's assessment of Rowenta. Distinctly better quality than others that I have tried (i.e. Sunbeam, Black and Decker and other typical U.S. based brands, though they are all made in China now.) Better is defined by quick and even heat across the full surface, which leads to faster and easier ironing. Never had a problem with dependability.

Rowenta for consumer model. If you sew or quilt and have the room, it may be worth investing in a commercial grade steam iron and just using batting covered with muslin stapled to a tabletop for ironing. This, for example.

Rowenta Steam Station. There's a separate reservoir for water which is great, so you don't have to fill it up everyday and it creates excellent even steam.

If you don't care much about that you can save money and get a basic Rowenta consumer model.