There is very little you can modify to make your mower last longer but a better air filter is definately one of them.
As a tech, I see a lot of mowers and I pull down a lot of engines,
You can see the difference, particularly on the ZTR's & RER's where the engine lives in the dust storm raised by it's own blades.
Add a bagger and it gets a lot worse.
The mowers with a donaldson type of filter are always clean inside, the others are seldom clean.
The big problem with fitting a canister filter is where you put it.
Most mounting kits bolt it onto the blower housing and make removing the blower housing very difficult.
I had refitted a couple onto the ROPS which of course requires a longer tube but the ones done like this have never needed a new filter element.
The ones fitted to the blower housing use about 3 outers to each inner generally 1 or 2 outers per year.
This will of course vary greatly depending upon what you mow but you just can not get your air intake far enough away from the blades.
In 1956 the local push mower makers fitted snorkels on their mowers with the air intake at the top of the handle bars.
These filters almost never need replacing where as the filters of the equivalent B & S engines rarely last a season before they clog up .
The only problem I regularly get with Honda engines is "it won't rev & blows black smoke" which is always a blocked air filter.
For 15 years Honda was forced to fit snorkels to the push mowers they sold down here.
We also made a snorkel to fit on the B & S Sprint series of engines and it is not uncommon to find one that is 40 years old and still running well on it's original bore.
The ones fitted with the over carb foam filters are always polished smooth in side with well worn bores, many of them quite new .
I bought a box of oversized pistons for the Victa 125cc two stroke cheap from a mower shop that was closing down.
The box was dated 1962 and there were 10 of the original 12 still in the box.
The owner said the only time he had to bore an engine was when the customer had used strait fuel and not premix.
So yes they are expensive and cost more than 50 regular filters , but 50 regular filter will not clean the air anywhere near as well.