1) Yes, the battery life is less. The better tablets have around 8-10 hrs of battery life.
2) It really depends on the person. Some people say it doesn't matter to them, others say it does.
Personally, I find that reflowing the text is still unsatisfactory for me because it gets page numbers/footnotes mixed in with the text, deals with line breaks and paragraphs poorly, and screws up tables and charts, but YMMV (it also depends on what methods were used to create the PDF. If it was created from a word document, it may convert reasonably, but if it is just OCRed from a scan, it might not). If what you have is just pure text narrative, like a novel, it may be ok for your purposes. Try putting your pdfs through Calibre (convert from pdf to epub or mobi) or Mobipocket Creator (pdf to mobi), view them, and see what you think.