How does iCloud and photo stream work?

I had an iPhone 4 and never downloaded the iCloud control panel to my computer (I have a PC) so I never really cared but I noticed that i had the ability to keep 1000 photos on my phone, anymore than that then the phone would delete a photo to make room for another one that I took. Well I got an iPhone 5s and downloaded the control panel and was just wondering how many photos I could keep if I always keep the photo stream backed up on my computer? Will my computer only keep 1000 as well? I have them set up to automatically save to the computer through the control panel but do I have to constantly connect my phone to make sure they are getting saved or will they go away after 30 days if I don't connect my phone. I know this kinda seems like a dumb series of questions but I just don't know and my usual tech guide is currently in bootcamp.

Cloud storage is where you have a folder online to store files. It's a bit like having a hard drive/memory stick, but it's on the web. The number of photos you can keep will depend on how big the image files are, and how much storage you are given. Without knowing these figures, there's no way to tell. For example, if you get 2GB of storage on the cloud, and your photos are 6MB each then do the maths: 2GB=2048MB, and 2048MB/6MB=431 images

That's how it works. And no they don't delete your images. The only person who can do that is you.