For mountain biking, or any riding where your chain is exposed to dirt, sand etc, how do you know when to replace the chain? I've heard 2 theories:
1. Wait until the chain is slipping off the sprocket and then replace both the chain and sprocket. The chain wears to that sprocket.
2. Replace the chain frequently and have a sprocket that last a whole lot longer.
Both ideas make sense and it almost seems like personal perference. I'm temped to go with the 2nd as my sprocket appears to be in descent condition--the non-shifting teeth don't have rounded edges. How do you know when it's time to replace the chain? Currently mine seems to have a bit of lateral flexibility, which I've heard is a sign. Also, what advantages are there of more expensive chains than cheaper ones? As far as I know, the chain it's job as long as it isn't slipping off or breaking. It seems like it would be better to buy inexpensive chains and replace them frequently.
Thank you for the help.