what are the chances?

i am 27M in relation with 28F. we are not planning to marry for next 2 more years, mostly due to financial constraints and career instability. we will grind for next 2 more years and then get married.
however, i get this doubt about my girl losing her fertile age gradually. i mean she will be around 30 year old then. what problems can we face regarding conceiving babies. i mean how realistic is it to expect 2 babies in that age naturally?