Do implied odds go down each round?

I have never heard this concept before and I wanted to make sure my logic isn't faulty.
This question is kind of directed towards no limit hold'em but I think it applies to all forms of poker.

In general are your implied odds on the flop (or earlier street in other forms of poker), better than the implied odds on the turn? Let's say you have a straight draw and you make your straight on the turn. You now have two turns of betting to build the pot whereas you would have one turn of betting if you made your straight on the river. So I would logically think you could call a little bit bigger bet on the flop because of the little bit larger implied odds then you could on the turn.

Did I miss something here?