Dad’s short answer: Three consumables: rollers, filters and cleaning solution. Rollers are the big one — expect to replace one every four to five months with regular use. Check that your model's parts are actually available before you buy.

The three consumables

Rollers wear out. The fibers pack down and stop scrubbing, and a tired roller is a common reason a machine seems to have gotten worse. Four to five months is what I see with regular use on most models.

Filters need replacing periodically too, and they're cheap. A clogged filter restricts airflow, which cuts your suction, which brings back the streaking problem.

Cleaning solution is the one people over-buy and over-use. Follow the dosage — more is not better, and excess detergent leaves a film that makes floors worse over time. Some machines work perfectly well with much less than the bottle suggests.

Run the parts check before you commit

This is the same advice I give on robot vacuums and it matters just as much here. Before you buy any model, search for its replacement roller and filter and confirm you can actually get them today.

Some brands keep the full catalog stocked for years. Others quietly exit the category and leave owners with a machine they can't service. A floor washer you can't get a roller for is a floor washer with a four-month lifespan.

It's also worth checking whether tested generic equivalents exist. On popular models they usually do, and they're often perfectly good.

Dad’s Take: Look up the replacement roller before you buy the machine. Two minutes now saves you a dead machine later.