Well there are a couple of strategies for this.
If you have unique images and content for your products you don't really need to worry about "google freshness" and no need to update weekly or anything like that
what you should be doing is:
1. IF your products are as unique and as informative as they can be you should be putting your effort on tweaking your category level pages. Doing basic keyword research and tweaking the data to get as much exposure for that category page as you can and ensure it's relevant.
2. Assuming you do not have a product specific Q&A page you should look at what product questions or product issues people are searching for within the google question box or "People also asked:" and then structure some Q&A information around that this will not only help your product provide relevant information but may also help you nab a few featured positions as well as looking "fresh"
Some ideas on this could be:
Washing a product at a specific temperature, inform the user that they can if so what effect if any will it have make sure it's at least 2-3 sentences in length.
If it's computer related write about what upgrades that are and are not possible. Link internally to these products if you have them.
If you do this you need to format it be a typical Q&A looking bit of content.
3. Ensure product page is formatted correctly tables have table titles all information is present that the user will need for that content and more importantly formatted use bullets where needed, tables where possible, correct text and image formatting.
That's about it for a "free" post on a forum
Hope that helps!
