Quiet tires are happy tires - meaning the more you abuse them and make them squeal, the faster they will wear down. Driving smoother means longer lasting tires. But you don't want to make them completely silent or you won't be driving as fast as you should, just try not to let them scream too much.
Noise is not a direct indicator of speed either. You may find that you actually get some faster laps by keeping the car balanced a bit better and not exceeding the limit of grip. Endurance racing is all about the compromise of keeping a good pace vs not wasting time by making mistakes or by using up your equipment too fast. Making mistakes also tends to ruin your tires a lot faster so it makes things even worse.
But Racing Soft tires will not last too long on any track because they are, well, soft. Softer rubber means more grip but a much faster rate of wear. They are usually the fastest overall, but they mean lots of pit stops. Hards will get you a few more laps between pit stops which makes the driving a bit more pleasant. When I ran the Suzuka endurance race I was able to get 12 laps out of Sports Softs(without completely using them up), so I wouldn't be surprised if you can go 9 or 10 laps on Racing Hards.
EDIT: I got 12 laps on SS with a Super GT GT500 car, the Toyota 88c-v will surely burn them up faster due to having so much power. But it's so fast it shouldn't be a problem. Don't drive them until they go to zero, you'll have some horrible laps. The AI pits when they reach about 20%, it seems to be faster to actually pit a little before that.
