Is there an expiry on bit.ly or tinyurl shortened URLs?
I'm asking because I'm thinking of persisting these shortened urls into the db for a client's twitter service.
UPDATE: if you keep sending bit.ly the same URL, it'll return the same shorten URL!, this is great, because it means I don't need to persist the shorten URLs in my database, and just cache bit.ly/shorten calls instead.
I was really hoping to avoid persisting shortened URLs in my db.
No. They'll remain valid as long as the service remains up.
Tinyurl says in the first paragraph on their main page that their urls "never expire": tinyurl.com. As @Peter J points out, that means it's only good as long as the company is in business and offers the same terms, but it's something.
This Bitly help page also states that their urls won't expire.
Daniel explained his answer correctly, but I believe the answer should be "yes". They will expire when the service decides to insert ads before redirecting you, or they begin charging for the service.
There is no guarantee whatsoever that your URL will be valid tomorrow.