It varies a lot. Some will send quarterly updates while others will maybe send something yearly. It's rare for a startup to spend a lot of time generating reports for seed investors. If you are on the board, then that's a totally different story.
Usually, seed investors have a "fire and forget" type of approach to their investments (since it's usually small, well at least small compared to VC). Your best bet would be to talk to the CEO and ask him for what you want. If it's not too much of a problem, you will probably get it.
Whatever your information rights are as a seed investor, ideally you should not be asking for any information that is not already generated and consumed by the management team to run the business. If you understand the business you have invested in well enough, then management reports will be useful and informative and won't require any additional work on the part of the management team. If you do not, it is a big imposition on a team to create specific reports for investors when they are entirely focused on launching the business and may not yet have resources they can dedicate to reporting.
That being said, it is good practice for any startup CEO to get into the habit of producing regular updates for investors-- even at early stages. Here is a pretty good description by Joel Spolsky of what that might entail.