product feeds for Amazon MWS

I am developing a solution for integrating Amazon MWS with our systems and have come up against a constraint with the submission of feeds using the Feed Api. At present submitting a product to Amazon takes up to 2 minutes per submission.

For example:

0-2 minutes _POST_PRODUCT_DATA_
0-2 minutes _POST_PRODUCT_PRICING_DATA_
0-2 minutes _POST_PRODUCT_IMAGE_DATA_
0-2 minutes _POST_INVENTORY_AVAILABILITY_DATA_
0-2 minutes _POST_PRODUCT_RELATIONSHIPS_DATA_
0-2 minutes _POST_PRODUCT_OVERRIDES_DATA_

This equates to up to 12 minutes per product submission and up to 10 minutes per update of product information when the product is already in the inventory. At present we are only submitting one product at a time, with the intention of submitting bulk inventory listings at a later date. Their documentation does state that server load can effect this (more so during peak times) but if it can take up to 12 minutes per product listing then I dread to think how long it would take to submit lets say 3000 or even 12000 new products to a marketplace in a bulk operation.

So my question is this:

Is there any way of speeding up this process or is this a limitation on Amazon that we can not get around?

As an after note. I am using the C# Api and posting using the XSD method, not the flat file method