pluralities: I do use tumblr stalkr, although not too frequently! I'm logged in on my iphone as well as my computer, though, which might be part of it. Thanks for the help :)
You may be surprised, but as long as you’re not logged out every time you post, it’s probably because of that combination.
Here’s a more detailed answer that you can completely ignore if you like:
When you log into Tumblr, you get a cookie. That validates everything you do with Tumblr on said device. Your computer has a cookie that validates your Tumblr actions on that computer. Your iPhone has a cookie that validates your Tumblr actions on your iPhone. Tumblr Stalkr creates and destroys a cookie every time you check in (I don’t want to hold onto something that can give me access to your account, of course).
Tumblr allows X number of cookies to be valid at a given time, which makes sense when you log into multiple computers or mobile devices to check Tumblr. But eventually a cookie expires, Tumblr Stalkr burns through valid cookies, or what have you and a cookie can become invalid. Same with logging into multiple devices.
That is why you’re logged out on occasion.
War hero, physics professor, liar.