[R] Accelerated failure time interpretation of coefficients

[Philipp Rappold]

I have one more conceptual question though, it would be fantastic if 
someone could graciously help out:

I am using an accelerated failure time model with time-varying 
covariates because I assume that my independent variables have a 
different impact on the chance for a failure at different points in 
lifetime. For example: High temperature has a different impact on 
failure in earlier years than in later years (for whatever reason). 
So far so good (hopefully).

But: From my regression I only get one coefficient for each 
independent variable and I am wondering how this "one" variable 
reflects the above mentioned time-dependent impact of my variable. 
Shouldn't I be getting a coefficient for each year of lifetime, 
which tells me exactly what impact a variable has in a given year?

I'm pretty sure I am totally mixing things up here, but I really 
couldn't find any helpful information, so any help is highly 
appreciated!!

Thank you very much!
Best
Philipp