I use 6 out of 8. I win! I probably download an app a month, but I also probably do 90% of my interneting on my phone.

I download tons of them so couldn't say with any accuracy how many a month.. but (and that's a big BUT) how long those apps get to stay on my device is a totally different story :)

I'm a bit of a gadget freak, so if I see something on the Apple App Store for my iPhone or Ipad that catches my eye for some reason, I'm highly likely to download and check it out. That said, unless I think I'll be using it very often, it generally won't last on my device for longer than 30 to 60 minutes as my curiosity about it would have been satisfied.  I currently have about a dozen apps I frequently use on my iPhone.. a few more on my iPad.  The most used app on both would have to be Audible Listener (https://itunes.apple.com/us/app/audible-audio-books-original-series-podcasts/id379693831?mt=8) App because I'm an avid audio book listener and I buy > 90% of the books I own from audible.com

The next app that will probably get used a lot is Transcend's "JetDrive Go" which gives me lots of options for the JetDrive 128GB additional storage iPhone/USB stick I recently purchased. Movies and audio books tend to take up a LOT of space and yes, my phone is already a 128 GB model 7 .. if they came larger than that I'd have definitely bought that instead. I'm always running low on space! lol :)

When looking for a particular type software to do something I'll probably download 5 or 6 if not more, but most will be deleted within 5 minutes
Apart from that in general maybe 1 a month on average. Generally speaking I know the app I'm looking to download be it a bank app, radio app or whatever.
Now when it comes to games, different story, downloaded so many to be just disappointed by what they are - try Temple Run, frustratingly annoying game but addictive (probably shouldn't be plugging it but it's free)