Marc Pitman says donor fatigue is a myth. He's right. Here's his explanation:
(Or see it on the web here.)
I believe there's another problem that gets falsely labeled donor fatigue: Fundraiser fatigue. We get sick of saying the same thing again and again (even though it may be working) so we change what we're saying to be more pleasing to our own ears. Or stop talking to donors entirely. When revenue drops, we blame it on the donors. Those fickle people have grown tired of our fundraising!
The solution to "donor fatigue": Keep on doing effective, relevant, donor-focused fundraising. That's the winning approach every time.