-People on here typically say that there LDs last about 10-20 minutes. Does the amount of time increase throughout experience.? Are there 3-4 year posters on here who can LD longer like an hour.?
It depends on the dream. Some of them only last a few minutes, while others are much longer. For the longer ones, it's hard to say how long they are in actual time. They may feel like they last hours, yet in reality you may have only been asleep for about half an hour. This is a good example.

-Does your recall improve with each LD.?
My recall seems to fluctuate randomly. Some nights I have amazing recall, while other nights I barely remember anything.

-Normally how long do your dreams last before you start LDing.? If it takes you awhile to perform a reality check, or realize your dreaming, do you discover that you LD a lot less longer.?
Again, it depends. Sometimes I catch dream signs right away, but other times I'm a bit more dense. I've never really noticed a correlation between how early I become lucid and how long the LD lasts.