Endorsers - Followup Thanks

Just wondering what marketing activities people followup with their endorsers.
I have 25 senior execs who have access to many markets.
I do know them all well - as I have worked with them.
Do I send them a gift for taking the time to read and endorse?
Do I follow up with a business meeting and ask for them to do some marketing?
Is there some protocol?
I don't want them to feel 'used' in any way - as they are relationships I have nurtured over the years.

I am so glad you are all here so I can ask these questions.
I feel I should know the answers...and I don't!

Thanks,
Rosalie