The most common thing i find is people setting their feed to daily, but this is not a good idea at all!!

When the Mambot sends the feed up to Google, it deletes/overwrites the last uploaded XML file. It then removes all the products from Google Base, and it takes about 24hrs to become active.

So if you have it set to every 24hrs, in theory you will probably never have any products live on Google Base, as just as they are live, you will find a new feed will upload over writing the last one.

Best thing I find to do, is to make 2 feeds, and staggered them both in time. So if you have one feed, such as "latest_products.xml" and set it to a number more than the amount of products you have in your store (like 9999 so it uploads all your products). and also set up "all_products.xml"

Now set them to upload every 4 days, but then stagger one of them to be 2 days different from the other. You can do this by adding 2 days onto the last run time stamp.

So
2008-03-14 17:06:22
Change it to
2008-03-16 17:06:22

So the system will count from that new date onwards, you could of course take 2 days off, but it makes no difference as long as the Mambot is counting 2 days different from the other feed.

Now Google Base, will have 2 copies of your products in their system, and as one is uploading and being updated the other has another 2 days to go before it is uploaded, by the time the first one has updated and is live, then the process will start again alternating between the 2.

Its a cheat, but it works

Regards
Ian

why would you want to update that often if items stay on base for a month before expiring?

Because many of my users who use this feed, update their website multiple times per day. So if your feed uploads on the 1st Jan at 1am, and they add a product at 2am that day, and you have it set to once every 30 days, it will be 31 or 32 days until that product is searchable, missing out on potential sales.

30 days for the next feed
+
1 or 2 days for the search to be organised by Google and published.

Personally, if Google published the feed instantly as it was uploaded, i would recommend uploading a feed once or more per day. But at the moment at least they dont, so it is better to do it as above