In the example you mentioned, a hardcoded value of 1 day is used but you can also inject a variable here, the same way you can do for service task parameters for example.
So you should be able to also specify something like #{x}ms (where x is a process variable containing the amount of ms, e.g. 10), or #{y} (where y is a process variable containing the entire expression, e.g. 10h).
Kris