1. You should update your community to keep them engaged and keep them donating (people can definitely forget to donate, and often appreciate quick reminders).
2. Your emails don't have to be exhausting or Pulitzer-worthy, a few words and a link can often do the trick
3. You don't just have to use email to update, other examples are included below:
Here Mark Dwight uses Twitter:

An Email update from Mark Dwight:
Subject: Please help me reach my goal for homeless youth
I'm sending this to a small group of friends to ask you a small favor. As most of you know, I'm riding my bicycle to the TED conference in Long Beach-- 500 miles in 5 days, starting next Wednesday. I'm using the ride to help raise money for a homeless youth outreach program here in SF called At The Crossroads. I'm $600 shy of my $5,000 goal, and I would really appreciate a small donation. The folks at ATC are just as excited by the number of donors as they are by any amount you donate. Really, no amount is too small. If each of you kick in $20 to $50, I'll reach or exceed my goal. It's super easy. Just follow this link...
http://atthecrossroads.org/campaign/markdwight
Thanks!
-Mark
A quick one of mine:
Dear Friends,
Thanks so much to everyone who has donated to my Campaign!
I've passed the halfway mark to my goal and have been working VERY hard not to be sarcastic. Unfortunately for me, I am failing quite often. Fortunately for you, I have been keeping up with my apology notes here:
http://atthecrossroads.org/campaign/rachelfletcher
It's not too late to donate for homeless youth!
Rachel
And a Facebook post:








