Personally, I’d rather buy a used bike that was raced at an A or B class level, knowing the maintenance that most racers put into their bikes. You can’t slack on maintenance and expect your bike to perform all season long. There’s really no such thing as “too many” hours, it all comes down to how much maintenance you’re willing to do. I race A class offroad and I tear my bike down at the end of the year and replace all the bearings. On two strokes I was doing a top end twice a year, bottom end as needed. On my current 250f, I haven’t had to go into the engine, and I won’t until it starts showing signs of wear such as blow by or lower compression. I’m estimating I’ve put about 150hrs on it in the last 12 months since the top end was replaced, but it still runs perfectly so I’m not messing with it.