Washer supply hoses come in different lengths. Using a longer water supply hose won't impair anything.
Sometimes these owners manuals are written by people who know less about the washing machine than the customer. When they tell you that the water supply hoses shouldn't be longer than 42 inches, it's mostly because the hoses they supply with the washer are 42 inches long, and they don't want to admit the only reason they supply such short hoses is because the longer ones cost more. So they tell some kid that there's a highly technical engineering reason why the hoses need to be short, and he writes that into the owner's manual. Maybe tear out that page and throw it in the garbage where it belongs.
Buy some longer hoses, and:
A) pay a bit more and get the ones from Fluidmaster that have the stainless steel braiding on the exterior. You should be able to find them at Reliable Parts if you live in Canada, or any good appliance parts store.
Washer supply hoses have been known to burst, and when one does burst it can cause an awful lot of water damage is the homeowner is away on vacation or doesn't get home for another 8 hours. When such bursts occur, it's usually because the rubber hose has been rubbing against something steel for a long time, and that has weakened the hose in one spot. Most people are not aware of this, but stainless steel is much harder than regular mild steel that the washing machine cabinet is made out of. So, if a hose with a stainless steel braided jacket on it rubs against something, it's that something that gets worn away, not the stainless steel.
B) Get some stainless steel strainer screens to go into the hose to strain any sand, rust or dirt out of the water before it goes into your machine. Those small pieces of dirt can cause the water mixing valve inside the machine to leak.
C) Turn off the water shut off valves to your washer whenever you're going on a vacation. I've never heard of a stainless steel braided hose bursting, but it's just a good practice to get into.