I am curious how many miles other Sprint GT owners are getting out of their original chain and what maintenance rituals you follow.
I'm at 48,000 kms (30,000 miles) on my factory Sprint ST chain. Chain is still OK, but starting to pick up some tight and loose spots. Rear sprocket still looks fine, but front 19 tooth sprocket is starting to show noticable wear. I'm likely good for a couple of thousand more k's, but will likley replace the set at about 50,000 kms. I'm pretty pleased with the life. I think the 19 tooth front sprocket really helps the life of the system.
I use spray chain lube at the end of every ride, usually 500-800 kms. I wipe the chain down with a solvent soaked rag every 2 months or so, and remove the front sprocket cover once or twice a year and clean both sprockets and the chain with a good solvent soak and brush. Messy, but it cleans things up well.
I use Esso Varsol 3139 solvent, which doesn't harm the o-rings. This is standard petroleum cleaning solvent, with a boiling range of 310-390 deg F (therefore the 3139 label). For chainlube, it is whatever I can find at a decent price that will fit in my tankbag. I have used Castrol, PJ-1, Bardahl, etc.