AZ, how have you charged your 305 over the course of its life? Lithium Ions do best if they are kept fully charged as much as possible. I've never had battery issues with my 305s (first one simply started to fall apart at the seams when it was about 3.5...replacement is kind of a POS).

Cadence sensor works perfectly...not sure about the HRM. I've never actually used the HRM with the 305 (I should sell my unused HRMs on eBay).