I have a refundable ticket and am not yet 100% sure of my arrival or departure date. However, I know the earliest arrival date and latest departure date, both which are less than 3 months from today. Is there any reason not to use these dates and will there be a problem if I arrive later or leave earlier? If I use exact dates but arrive earlier, I assume that would be a problem. Right?

My TA recommended ZVS (Zierer Visa Service) http://www.zvs.com/ at a cost of $209 for two of us. Is that a competitive price and is it a good service? I saw someone near the start of this thread had used them.

Thanks.