I had the same problem with the PBSF Turbo but only after I used it for a few weeks. Luckily I kept the receipt and I was able to get it replaced from the store where I bought it. Mine would turn off after 10 to 15 minutes of riding. Initially I thought it might be because of vibrations on the road so I left it on one time after I came home. It still turned itself off so it was definitely a defect.

I also have a Radbot 1000 which is my main tail light. The PBSF is the back-up. No problems with the Radbot except that the batteries need replacing more often. I have since started using rechargeable AAAs.