It's just plain false economy to think that you're saving money by delaying maintenance with a Grand Prix bike. When I got my RS125, I didn't really know the exact service history of the engine. I made the decision to run a top end through it then pull it down for a rebuild. As luck would have it, after that first top end, all signs were pointing towards a rebuild. So here I am, I've ordered all I need to make sure this engine will be reliable. A number of people have asked about 125GP costs, so just as FYI, 50 items from Honda, imported from Japan cost me about NZ$810. This excludes approximately NZ$220 for a piston top end and assuming your cylinder is still good to go. So around $1,050 - $1,300 (when you include misc items) for a almost completely fresh engine, including crank!
Lots of riding experience will make you fast but without preparation, ill reliability will hold you back from getting that experience. Hopefully by going through this now and starting a full maintenance schedule on the engine, I'll be placed for continued progress. With any luck I'll be able to fight closer to the front knowing I have a solid bike under me.