Can a single SharePoint Designer workflow run concurrently on a single item?

Question

I have a document library and simple workflow I created in SharePoint Designer that runs automatically when the item is created AND automatically when the item is changed.

The workflow will pause of a long time (up to 90 days) and then send a reminder email which gets sent only if the "expires date" field has been met.

Users are allowed to change the expire column any time.

Questions:

1. Since it is a single workflow, can it be activated multiple times on a single item? (e.g. if the document was edited twice, would there be three total workflows running?)

2. If multiple workflows are created, and they run even if the document exists, is there a performance issue I should be aware of? Will I be hammering the server if there are a lot of documents in our small farm?

Answer 1

1. No, there will only be one instance of a given workflow per item.
2. You should always consider performance, but the answer is really.. "it depends". If there are a LOT of documents (hundreds?) then maybe a console app or timer job scheduled to run daily is a more scalable approach.