Time Dependent Reliability -cumulative probability of failure

Hi All,

Thank you so much for the amazing uqlab software. I just need a clarification on how to approach two scenario in uqlab. For example , if I have a limit state function as shown below.

  g (X) = (X1 - 0.02t) (X2 - 0.03t). 
 Assuming X1 and X2 are standard normal distribution RV. 

What is the difference between computing the probability of failure at a given time say t=3yrs AND obtaining the cumulative probability of failure [0,3]?

In the first case, I will substitute t=3 and possibly use MCS to obtain the probability of failure. How does this differ from the determination of cumulative probability of failure [0,3]?

Appreciate thoughts on the difference in terms of implementation using MCS and uqlab.