Well, title says all? Let me know what you think, and also, if you do keep track on when the spiders come, what would be the value for that?
I haven't ever really been too concerned about it because I don't have dynamic or content related sites. However, I found this link that might be of some assistance: http://www.google.com/support/webmasters/bin/answer.py?answer=34439&topic=8843 I wouldn't think that it would actually make much of an impact on where your website ranks, but it may cause delays in your websites SERP's changing based on changes / improvements you have made.