90k is the recommended service mileage for the timing belt for your car. I'd stick with that.

Your friend is gambling with the life of their engine. You could do the same thing and it's not really a question of part quality, it's about recommeneded maintenance schedules. You could gamble just as much as they are, but is the cost of replacing the timing belt/water pump all that much in comparison to the price of replacing bent valves, dented pistons, and the timing belt/water pump if the belt breaks? Only you can make that decision.

Consider taking it to the dealership and just have them inspect the belt. They may clear you for another 20k mi on that belt depending on its condition.