I'm wondering the same thing. I'm ttc #2 and bloody knackered having dtd every other day since last thursday (4 times in a week!!! Thats ridiculous!!!). My OH was very not in the mood last night and although we managed it, there wasnt exactly much, ahem, man juice to go round! He was like - the tank is empty!!!!! So I REALLY hope we have managed it this month, it is starting to feel a bit like a chore. I think next month we might start later in my cyle, and maybe try and go for every third day too. I think whatever you do/however much you do it you probably dont feel like you've done enough when you're in the 2ww and wishing you'd just got one more session in to try and seal the deal! ;-)
lots of luck to you!! x