Umm... everyone here has definitely given you LOTS of good advice! I generally replace chain/cassette each season for my customers that ride 3000-5000 miles. As someone else mentioned, the chainrings generally get replaced every 2-3 years... it simply depends on the care of the bike from the customer and the quality of the rings... some people are fortunate to have them last a bit longer. As for tires, it generally depends on what type of tires you run and the mileage that you ride.... perhaps replacing them once a year if you continue riding the amount that you did last year. The rain can definitely have a LOT to do with how everything lasts, be sure to wipe everything done after a wet ride, take a file and file down your brake pads to get any of the debris out etc...

Personally, I haven't changed brake pads in 3-4 years, change the chain every 1500 miles which generally allows me to replace the cassette every other time, tires get replaced a couple of times a year, and the chain rings have nOT been replaced yet.(5 years old)

Good luck with the remainder of the season and hope everyones advice helps!