My FS told us to DTD every day or every second day when I'm at my most fertile (for about a week). So I'm sure everyday is fine, but if you can only manage every 2nd then that's still good. In fact, we missed my ovulation last month, but the FS said that was okay as we covered the day before and after.

Also, I read in a book (can't remember which!) that it's good to DTD regularly throughout the month and not 'save' it for when you O. The reason being that sperm do live for a number of days, but they are stored in your DH, so if you leave it for weeks then DTD when you O you're not getting the best quality fresh sperm as you have to go through the older stuff first! LOL Whereas if you do it regularly you are getting fresher sperm, that are a bit healthier and more likely to get to the finish line. :-)