Aggregate events over a large period of time maintaining previous task maps

Hi all, I am new to logstash and aggregate - but not too event sourcing/CQRS and I am looking for a strategy to handle the following problem.

I have a product.created that contains the initial available products.
I then have consecutive stock.updated that contain increments/decrements of the quantity.

I am using the aggregate plugin but I am struggling to see how this would work in case the product created product comes way before the updates.

From what I see every time aggregate times out it evicts the map and this is a problem for me cause when I receive an update I am always going to need the previous result (kind of like doing a reduce over the events).

I was wondering if there is a way not to evict the map? Am I doing it right?

Thank you in advance for all your answers.