Nunca/siempre and the preterite/imperfect

[dupond]

The way I understood it was that the choice between the preterite and imperfect depends on whether the action can be placed in a definite time frame.

So in the case of the rent, you'd say, "Nunca tenia dinero parar pagar la renta," if you had in mind a general statement. However, if this was a tenant who'd been evicted after say, five months, you'd say, "Nunca tuvo dinero parar pagar la renta," since you'd be talking about a specific time period.

I thought the same would apply for "siempre". The imperfect might go more readily with "siempre" since most times you'd be describing an ongoing action. However, you might use the preterite if you were referring to an action that took place regularly or for the entire duration of a given time period, e.g. "Siempre hizo calor cuando visité Madrid."

Have I understood it correctly?