Inspect and maintain what you have. If you find something keeps breaking, requires constant adjustment or just plain bothers you, then go to the local bike shop, discuss your issue intelligently, identify your budget and determine if worth investing the time/budget to "upgrade".
You get three options in most situations, but really can only have two.
1. Low-maintenance/longevity,
2. Cheap, and
3. Lightweight.
Choose wisely for your situation.