As is applicable to all non-final variables, you can reassign value to inferred variables. Just ensure that the reassigned value matches its inferred type. In the following code, since the type of the age variable is inferred as int, you can't assign a decimal value of 10.9 to it. Similarly, since the type of the query variable is inferred as StringBuilder. The type of a variable is inferred just once, as follows:

var age = 9;     // type of variable age inferred as int 
age = 10.9;      // can't assign 10.9 to variable of type int 
 
var query = new StringBuilder("SELECT");         // Type of variable 
                                              // query is StringBuilder 
query = query.toString() + "FROM" + "TABLE";     // won't compile;  
                                                 // can't assign String                                                                                                 
                                                // to variable query