I recently started road biking, and I accumulated about 400 miles on my new bike already. Any of you have an idea what I need to keep an eye out for? I have a couple specific questions~ please help

How many miles does the tire last? (generally or average)
How many miles does the wheel last? (Shimano R550)
When do I need to replace the chains? do I replace them with the cassette? and crank rings?

I've been wiping off the chain and cassettes every 70-100 miles and re-oil them. I hope that's good enough

In addition, do you recommend cutting a carbon seatpost to save some weight and dimension issue? Since the seat tube can't retract fully into the frame. btw~ I customized a bike carrier in my X to carry the bike around~ if any of you are interested, I can post some pics~ thanks you guys for all the info!