i could never let my blades go that long!!!!
i love fresh razor sharp blades. the new toro blades might last two days, but dont know. i dont have much experience using the hardened blades, our kubota blades fromt eh factory are hardened, but we like the aftermarket better with low lift and they are not hardened.
anyways, i think after 8 hrs on any amount of lawns on regular blades is time to sharpen. there is alot of guys here that only sharpen once per week too. i dont get it, these guys lawns have that white appearance after cutting due to the dullness.