What follow a preposition?

Hi,

I was taught in my primary school that only a noun, pronoun, noun phrase, gerund or relative clause can follow a preposition, acting as a "prepositional object".

Yet, recently I saw a sentence below that confounds me so much.

"We are going to keep the ostrich-leather bag for AS LONG AS OUR FAMILY EXISTS."

Here, "AS LONG AS OUR FAMILY EXISTS" is right after the preposition "for", is it a prepositional object? or should it be regarded as a prepositional object?

Many thanks.