All my life! Probably first with feces, but that's only speculation ;P
Seriously, I guess since high school, 14 yrs old. So over 15 years. I've been not so prolific these days, but I want to get back into it. Today I get my easel back, so we'll see! I have a graphics tablet, so I've been doing more drawing than painting.
Wow - these are beautiful. How long have you been painting?