what would you do with a brand new one that you intended to keep for life, to prevent the deck from rotting?
Propper care and maintenance goes a long way.
1. Replace steel bolts. One of the most painful things I've encountered is having a seized bolt in a mower, be it alloy or steel based. It might seem like a lot of work, but if you ever need to take that component off again in the future, hopefully, it won't have rusted and you won't break a bolt and have to drill it out (I know I've had to).
2. Where possible, mow a dry lawn
3. When you're finished mowing, clean out the underside of the mower
4. Run the mower at full speed for 2-3 minutes with the catcher off to circulate air under the mower and dry it out
5. If you're a bit more pedantic, you can dry the underside with a rag. If you notice any rust or unpainted spots, wipe a layer of protecting oil on it. WD40 will work in a pinch.
6. Pay attention to other steel components, like the muffler, bolts, and springs/hinges for the catcher flap. Do not oil the muffler, you'll find out why the next time you start the mower haha. But you could use some heat resistant paint to spray the outside of the muffler once cleaned and dried, along with the retaining clips. This also helps keep the new look of your mower.
7. Do not leave the catcher attached during storage. In warm or slightly humid storage locations, the moisture from the grass in the catcher can have an effect on the steel.
8. Store the mower out of direct sunlight, in a cool dry place where possible, preferably sheltered (Like a shed or garage). If the storage location isn't watertight or is prone to moisture buildup, you may want to put some moisture absorbing crystals in there to absorb the moisture from the air.
9. Again, if you're pedantic, you can coat the plastic components in a UV resistant coating. This will help to prevent fading of the plastic if the mower is exposed to the sun for extended periods of time, again keeping your mower looking newer.
I had a bloke come here today with his father because his father wanted a mower as the son had bought one from me a couple of years ago. When I asked him what mower it was all he could tell me was that it was green, as then asked him if it was a 2 stroke or a 4 stroke and all he could tell me was that he thought it was a 4 stroke
I died a little inside reading that...
